Tabs are invisible in latest Nightly

### Describe the bug

Tabs are invisible in latest Firefox Nightly.

### Expected behavior

_No response_

### Screenshots


### OS

Others

### OS - Others

Windows 11 23H2 64-bit (Build 22631.2361)

### Firefox Version

FX Nightly v121.0a1 64-bit

### Distribution

- [X] [Original Lepton](https://github.com/black7375/Firefox-UI-Fix)
- [ ] [Lepton's photon style](https://github.com/black7375/Firefox-UI-Fix/tree/photon-style)
- [ ] [Lepton's proton style](https://github.com/black7375/Firefox-UI-Fix/tree/proton-style)

### Theme

- [X] Light
- [X] Dark
- [ ] Alpenglow (System: Light)
- [ ] Alpenglow (System: Dark)
- [ ] System Default
- [ ] Others: (e.g. [Photon Colors](https://addons.mozilla.org/en-US/firefox/addon/photon-colors/), [Google Chrome Dark](https://addons.mozilla.org/en-US/firefox/addon/google-chrome-dark/), [Fairytale Of Nature](https://addons.mozilla.org/en-US/firefox/addon/fairytale-of-nature/))

### Theme - More Info

_No response_

### `user.js` setup

user.js setup

```javascript
// ** Theme Default Options ****************************************************
// userchrome.css usercontent.css activate
user_pref("toolkit.legacyUserProfileCustomizations.stylesheets", true);

// Proton Enabled #127 || Removed at 97 #328 (Maintained for compatibility with ESR)
user_pref("browser.proton.enabled", true);

// Fill SVG Color
user_pref("svg.context-properties.content.enabled", true);

// CSS Color Mix - 88 Above
user_pref("layout.css.color-mix.enabled", true);

// CSS Blur Filter - 88 Above
user_pref("layout.css.backdrop-filter.enabled", true);

// Restore Compact Mode - 89 Above
user_pref("browser.compactmode.show", true);

// about:home Search Bar - 89 Above
user_pref("browser.newtabpage.activity-stream.improvesearch.handoffToAwesomebar", false);

// CSS's `:has()` selector #457 - 103 Above
user_pref("layout.css.has-selector.enabled", true);

// Browser Theme Based Scheme - Will be activate 95 Above
// user_pref("layout.css.prefers-color-scheme.content-override", 3);

// ** Theme Related Options ****************************************************
// == Theme Distribution Settings ==============================================
// The rows that are located continuously must be changed `true`/`false` explicitly because there is a collision.
// https://github.com/black7375/Firefox-UI-Fix/wiki/Options#important
user_pref("userChrome.tab.connect_to_window", true); // Original, Photon
user_pref("userChrome.tab.color_like_toolbar", true); // Original, Photon

user_pref("userChrome.tab.lepton_like_padding", true); // Original
user_pref("userChrome.tab.photon_like_padding", false); // Photon

user_pref("userChrome.tab.dynamic_separator", true); // Original, Proton
user_pref("userChrome.tab.static_separator", false); // Photon
user_pref("userChrome.tab.static_separator.selected_accent", false); // Just option
user_pref("userChrome.tab.bar_separator", false); // Just option

user_pref("userChrome.tab.newtab_button_like_tab", true); // Original
user_pref("userChrome.tab.newtab_button_smaller", false); // Photon
user_pref("userChrome.tab.newtab_button_proton", false); // Proton

user_pref("userChrome.icon.panel_full", true); // Original, Proton
user_pref("userChrome.icon.panel_photon", false); // Photon

// Original Only
user_pref("userChrome.tab.box_shadow", true);
user_pref("userChrome.tab.bottom_rounded_corner", true);

// Photon Only
user_pref("userChrome.tab.photon_like_contextline", false);
user_pref("userChrome.rounding.square_tab", false);

// == Theme Compatibility Settings =============================================
// user_pref("userChrome.compatibility.accent_color", true); // Firefox v103 Below
// user_pref("userChrome.compatibility.covered_header_image", true);
// user_pref("userChrome.compatibility.panel_cutoff", true);
// user_pref("userChrome.compatibility.navbar_top_border", true);
// user_pref("userChrome.compatibility.dynamic_separator", true); // Need dynamic_separator

// user_pref("userChrome.compatibility.os.linux_non_native_titlebar_button", true);
// user_pref("userChrome.compatibility.os.windows_maximized", true);
// user_pref("userChrome.compatibility.os.win11", true);

// == Theme Custom Settings ====================================================
// -- User Chrome --------------------------------------------------------------
// user_pref("userChrome.theme.private", true);
// user_pref("userChrome.theme.proton_color.dark_blue_accent", true);
// user_pref("userChrome.theme.monospace", true);
// user_pref("userChrome.theme.transparent.frame", true);
// user_pref("userChrome.theme.transparent.menu", true);
// user_pref("userChrome.theme.transparent.panel", true);
// user_pref("userChrome.theme.non_native_menu", true); // only for linux

// user_pref("userChrome.decoration.disable_panel_animate", true);
// user_pref("userChrome.decoration.disable_sidebar_animate", true);
// user_pref("userChrome.decoration.panel_button_separator", true);
// user_pref("userChrome.decoration.panel_arrow", true);

// user_pref("userChrome.autohide.tab", true);
// user_pref("userChrome.autohide.tab.opacity", true);
// user_pref("userChrome.autohide.tab.blur", true);
// user_pref("userChrome.autohide.tabbar", true);
// user_pref("userChrome.autohide.navbar", true);
// user_pref("userChrome.autohide.bookmarkbar", true);
// user_pref("userChrome.autohide.sidebar", true);
// user_pref("userChrome.autohide.fill_urlbar", true);
// user_pref("userChrome.autohide.back_button", true);
// user_pref("userChrome.autohide.forward_button", true);
// user_pref("userChrome.autohide.page_action", true);
// user_pref("userChrome.autohide.toolbar_overlap", true);
// user_pref("userChrome.autohide.toolbar_overlap.allow_layout_shift", true);

// user_pref("userChrome.hidden.tab_icon", true);
// user_pref("userChrome.hidden.tab_icon.always", true);
// user_pref("userChrome.hidden.tabbar", true);
// user_pref("userChrome.hidden.navbar", true);
// user_pref("userChrome.hidden.private_indicator", true);
// user_pref("userChrome.hidden.titlebar_container", true);
// user_pref("userChrome.hidden.sidebar_header", true);
// user_pref("userChrome.hidden.sidebar_header.vertical_tab_only", true);
// user_pref("userChrome.hidden.urlbar_iconbox", true);
// user_pref("userChrome.hidden.urlbar_iconbox.label_only", true);
// user_pref("userChrome.hidden.bookmarkbar_icon", true);
// user_pref("userChrome.hidden.bookmarkbar_label", true);
// user_pref("userChrome.hidden.disabled_menu", true);

// user_pref("userChrome.centered.tab", true);
// user_pref("userChrome.centered.tab.label", true);
// user_pref("userChrome.centered.urlbar", true);
// user_pref("userChrome.centered.bookmarkbar", true);

// user_pref("userChrome.counter.tab", true);
// user_pref("userChrome.counter.bookmark_menu", true);

// user_pref("userChrome.combined.nav_button", true);
// user_pref("userChrome.combined.nav_button.home_button", true);
// user_pref("userChrome.combined.urlbar.nav_button", true);
// user_pref("userChrome.combined.urlbar.home_button", true);
// user_pref("userChrome.combined.urlbar.reload_button", true);
// user_pref("userChrome.combined.sub_button.none_background", true);
// user_pref("userChrome.combined.sub_button.as_normal", true);

// user_pref("userChrome.rounding.square_button", true);
// user_pref("userChrome.rounding.square_dialog", true);
// user_pref("userChrome.rounding.square_panel", true);
// user_pref("userChrome.rounding.square_panelitem", true);
// user_pref("userChrome.rounding.square_menupopup", true);
// user_pref("userChrome.rounding.square_menuitem", true);
// user_pref("userChrome.rounding.square_infobox", true);
// user_pref("userChrome.rounding.square_toolbar", true);
// user_pref("userChrome.rounding.square_field", true);
// user_pref("userChrome.rounding.square_urlView_item", true);
// user_pref("userChrome.rounding.square_checklabel", true);

// user_pref("userChrome.padding.first_tab", true);
// user_pref("userChrome.padding.first_tab.always", true);
// user_pref("userChrome.padding.drag_space", true);
// user_pref("userChrome.padding.drag_space.maximized", true);

// user_pref("userChrome.padding.toolbar_button.compact", true);
// user_pref("userChrome.padding.menu_compact", true);
// user_pref("userChrome.padding.bookmark_menu.compact", true);
// user_pref("userChrome.padding.urlView_expanding", true);
// user_pref("userChrome.padding.urlView_result", true);
// user_pref("userChrome.padding.panel_header", true);

// user_pref("userChrome.urlbar.iconbox_with_separator", true);

// user_pref("userChrome.urlView.as_commandbar", true);
// user_pref("userChrome.urlView.full_width_padding", true);
// user_pref("userChrome.urlView.always_show_page_actions", true);
// user_pref("userChrome.urlView.move_icon_to_left", true);
// user_pref("userChrome.urlView.go_button_when_typing", true);
// user_pref("userChrome.urlView.focus_item_border", true);

// user_pref("userChrome.tabbar.as_titlebar", true);
// user_pref("userChrome.tabbar.fill_width", true);
// user_pref("userChrome.tabbar.multi_row", true);
// user_pref("userChrome.tabbar.unscroll", true);
// user_pref("userChrome.tabbar.on_bottom", true);
// user_pref("userChrome.tabbar.on_bottom.above_bookmark", true); // Need on_bottom
// user_pref("userChrome.tabbar.on_bottom.menubar_on_top", true); // Need on_bottom
// user_pref("userChrome.tabbar.on_bottom.hidden_single_tab", true); // Need on_bottom
// user_pref("userChrome.tabbar.one_liner", true);
// user_pref("userChrome.tabbar.one_liner.combine_navbar", true); // Need one_liner
// user_pref("userChrome.tabbar.one_liner.tabbar_first", true); // Need one_liner
// user_pref("userChrome.tabbar.one_liner.responsive", true); // Need one_liner

// user_pref("userChrome.tab.bottom_rounded_corner.all", true);
// user_pref("userChrome.tab.bottom_rounded_corner.australis", true);
// user_pref("userChrome.tab.bottom_rounded_corner.edge", true);
// user_pref("userChrome.tab.bottom_rounded_corner.chrome", true);
// user_pref("userChrome.tab.bottom_rounded_corner.chrome_legacy", true);
// user_pref("userChrome.tab.bottom_rounded_corner.wave", true);
// user_pref("userChrome.tab.always_show_tab_icon", true);
// user_pref("userChrome.tab.close_button_at_pinned", true);
// user_pref("userChrome.tab.close_button_at_pinned.always", true);
// user_pref("userChrome.tab.close_button_at_pinned.background", true);
// user_pref("userChrome.tab.close_button_at_hover.always", true); // Need close_button_at_hover
// user_pref("userChrome.tab.close_button_at_hover.with_selected", true); // Need close_button_at_hover
// user_pref("userChrome.tab.sound_show_label", true); // Need remove sound_hide_label
// user_pref("userChrome.tab.container.on_top", true);
// user_pref("userChrome.tab.sound_with_favicons.on_center", true);
// user_pref("userChrome.tab.selected_bold", true);

// user_pref("userChrome.navbar.as_sidebar", true);

// user_pref("userChrome.bookmarkbar.multi_row", true);

// user_pref("userChrome.findbar.floating_on_top", true);

// user_pref("userChrome.panel.remove_strip", true);
// user_pref("userChrome.panel.full_width_separator", true);
// user_pref("userChrome.panel.full_width_padding", true);

// user_pref("userChrome.sidebar.overlap", true);

// user_pref("userChrome.icon.disabled", true);
// user_pref("userChrome.icon.account_image_to_right", true);
// user_pref("userChrome.icon.account_label_to_right", true);
// user_pref("userChrome.icon.menu.full", true);
// user_pref("userChrome.icon.global_menu.mac", true);

// -- User Content -------------------------------------------------------------
// user_pref("userContent.player.ui.twoline", true);

// user_pref("userContent.newTab.hidden_logo", true);
// user_pref("userContent.newTab.background_image", true); // Need wallpaper image --uc-newTab-wallpaper: url("../icons/background_image.png");

// user_pref("userContent.page.proton_color.dark_blue_accent", true);
// user_pref("userContent.page.proton_color.system_accent", true);
// user_pref("userContent.page.dark_mode.pdf", true);
// user_pref("userContent.page.monospace", true);

// == Theme Default Settings ===================================================
// -- User Chrome --------------------------------------------------------------
user_pref("userChrome.compatibility.theme", true);
user_pref("userChrome.compatibility.os", true);

user_pref("userChrome.theme.built_in_contrast", true);
user_pref("userChrome.theme.system_default", true);
user_pref("userChrome.theme.proton_color", true);
user_pref("userChrome.theme.proton_chrome", true); // Need proton_color
user_pref("userChrome.theme.fully_color", true); // Need proton_color
user_pref("userChrome.theme.fully_dark", true); // Need proton_color

user_pref("userChrome.decoration.cursor", true);
user_pref("userChrome.decoration.field_border", true);
user_pref("userChrome.decoration.download_panel", true);
user_pref("userChrome.decoration.animate", true);

user_pref("userChrome.padding.tabbar_width", true);
user_pref("userChrome.padding.tabbar_height", true);
user_pref("userChrome.padding.toolbar_button", true);
user_pref("userChrome.padding.navbar_width", true);
user_pref("userChrome.padding.urlbar", true);
user_pref("userChrome.padding.bookmarkbar", true);
user_pref("userChrome.padding.infobar", true);
user_pref("userChrome.padding.menu", true);
user_pref("userChrome.padding.bookmark_menu", true);
user_pref("userChrome.padding.global_menubar", true);
user_pref("userChrome.padding.panel", true);
user_pref("userChrome.padding.popup_panel", true);

user_pref("userChrome.tab.multi_selected", true);
user_pref("userChrome.tab.unloaded", true);
user_pref("userChrome.tab.letters_cleary", true);
user_pref("userChrome.tab.close_button_at_hover", false);
user_pref("userChrome.tab.sound_hide_label", true);
user_pref("userChrome.tab.sound_with_favicons", true);
user_pref("userChrome.tab.pip", true);
user_pref("userChrome.tab.container", true);
user_pref("userChrome.tab.crashed", true);

user_pref("userChrome.fullscreen.overlap", true);
user_pref("userChrome.fullscreen.show_bookmarkbar", true);

user_pref("userChrome.icon.library", true);
user_pref("userChrome.icon.panel", true);
user_pref("userChrome.icon.menu", true);
user_pref("userChrome.icon.context_menu", true);
user_pref("userChrome.icon.global_menu", true);
user_pref("userChrome.icon.global_menubar", true);

// -- User Content -------------------------------------------------------------
user_pref("userContent.player.ui", true);
user_pref("userContent.player.icon", true);
user_pref("userContent.player.noaudio", true);
user_pref("userContent.player.size", true);
user_pref("userContent.player.click_to_play", true);
user_pref("userContent.player.animate", true);

user_pref("userContent.newTab.full_icon", true);
user_pref("userContent.newTab.animate", true);
user_pref("userContent.newTab.pocket_to_last", true);
user_pref("userContent.newTab.searchbar", true);

user_pref("userContent.page.field_border", true);
user_pref("userContent.page.illustration", true);
user_pref("userContent.page.proton_color", true);
user_pref("userContent.page.dark_mode", true); // Need proton_color
user_pref("userContent.page.proton", true); // Need proton_color

// ** Useful Options ***********************************************************
// Integrated calculator at urlbar
user_pref("browser.urlbar.suggest.calculator", true);

// Integrated unit convertor at urlbar
// user_pref("browser.urlbar.unitConversion.enabled", true);

// Draw in Titlebar
// user_pref("browser.tabs.drawInTitlebar", true);
// user_pref("browser.tabs.inTitlebar", 1); // Nightly, 96 Above

// ** Scrolling Settings *******************************************************
// == Only Sharpen Scrolling ===================================================
// Pref Value Original
/*
user_pref("mousewheel.min_line_scroll_amount", 10); // 5
user_pref("general.smoothScroll.mouseWheel.durationMinMS", 80); // 50
user_pref("general.smoothScroll.currentVelocityWeighting", "0.15"); // "0.25"
user_pref("general.smoothScroll.stopDecelerationWeighting", "0.6"); // "0.4"
*/

// == Smooth Scrolling ==========================================================
// ** Scrolling Options ********************************************************
// based on natural smooth scrolling v2 by aveyo
// this preset will reset couple extra variables for consistency
// Pref Value Original
/*
user_pref("apz.allow_zooming", true); /// true
user_pref("apz.force_disable_desktop_zooming_scrollbars", false); /// false
user_pref("apz.paint_skipping.enabled", true); /// true
user_pref("apz.windows.use_direct_manipulation", true); /// true
user_pref("dom.event.wheel-deltaMode-lines.always-disabled", true); /// false
user_pref("general.smoothScroll.currentVelocityWeighting", "0.12"); /// "0.25" <- 1. If scroll too slow, set to "0.15"
user_pref("general.smoothScroll.durationToIntervalRatio", 1000); /// 200
user_pref("general.smoothScroll.lines.durationMaxMS", 100); /// 150
user_pref("general.smoothScroll.lines.durationMinMS", 0); /// 150
user_pref("general.smoothScroll.mouseWheel.durationMaxMS", 100); /// 200
user_pref("general.smoothScroll.mouseWheel.durationMinMS", 0); /// 50
user_pref("general.smoothScroll.mouseWheel.migrationPercent", 100); /// 100
user_pref("general.smoothScroll.msdPhysics.continuousMotionMaxDeltaMS", 12); /// 120
user_pref("general.smoothScroll.msdPhysics.enabled", true); /// false
user_pref("general.smoothScroll.msdPhysics.motionBeginSpringConstant", 200); /// 1250
user_pref("general.smoothScroll.msdPhysics.regularSpringConstant", 200); /// 1000
user_pref("general.smoothScroll.msdPhysics.slowdownMinDeltaMS", 10); /// 12
user_pref("general.smoothScroll.msdPhysics.slowdownMinDeltaRatio", "1.20"); /// "1.3"
user_pref("general.smoothScroll.msdPhysics.slowdownSpringConstant", 1000); /// 2000
user_pref("general.smoothScroll.other.durationMaxMS", 100); /// 150
user_pref("general.smoothScroll.other.durationMinMS", 0); /// 150
user_pref("general.smoothScroll.pages.durationMaxMS", 100); /// 150
user_pref("general.smoothScroll.pages.durationMinMS", 0); /// 150
user_pref("general.smoothScroll.pixels.durationMaxMS", 100); /// 150
user_pref("general.smoothScroll.pixels.durationMinMS", 0); /// 150
user_pref("general.smoothScroll.scrollbars.durationMaxMS", 100); /// 150
user_pref("general.smoothScroll.scrollbars.durationMinMS", 0); /// 150
user_pref("general.smoothScroll.stopDecelerationWeighting", "0.6"); /// "0.4"
user_pref("layers.async-pan-zoom.enabled", true); /// true
user_pref("layout.css.scroll-behavior.spring-constant", "250.0"); /// "250.0"
user_pref("mousewheel.acceleration.factor", 3); /// 10
user_pref("mousewheel.acceleration.start", -1); /// -1
user_pref("mousewheel.default.delta_multiplier_x", 100); /// 100
user_pref("mousewheel.default.delta_multiplier_y", 100); /// 100
user_pref("mousewheel.default.delta_multiplier_z", 100); /// 100
user_pref("mousewheel.min_line_scroll_amount", 0); /// 5
user_pref("mousewheel.system_scroll_override.enabled", true); /// true <- 2. If scroll too fast, set to false
user_pref("mousewheel.system_scroll_override_on_root_content.enabled", false); /// true
user_pref("mousewheel.transaction.timeout", 1500); /// 1500
user_pref("toolkit.scrollbox.horizontalScrollDistance", 4); /// 5
user_pref("toolkit.scrollbox.verticalScrollDistance", 3); /// 3
*/
```

### Additional context

_No response_

The issue names no source file, test, or entry point. First reproduce the invisible-tabs report in Firefox Nightly using the supplied Windows 11, theme, distribution, and user.js setup, then inspect the tab styling involved. Done means tabs are visible again in the reported Nightly configuration and the relevant behavior is covered by an appropriate verification.

Written by the indexing model from the issue text.