Middle mouse button no longer opens new tab

### Guidelines

- [x] I have read [how to report a new issue](https://github.com/Aris-t2/CustomCSSforFx/issues/4)
- [x] I have used the [latest release](https://github.com/Aris-t2/CustomCSSforFx/releases/latest)
- [x] I have set the `toolkit.legacyUserProfileCustomizations.stylesheets` in `about:config` to `true`

### Does the issue occur without any files inside /chrome/ folder?

No

### Description of the Issue

When I click on tab bar with middle button new tab doesn't appear.
My Firefox is 146.0.1.
CustomCSSfoFx is 4.7.5
When I use version 4.6.2 this bug doesn't exists.

### Issue description, userChrome.css/userContent.css 'settings' the issue occurs with and steps to reproduce the issue

Just click on the tab bar with middle mouse button.

### Does the issue occur with the most recent version of CustomCSSforFx (release/test/dev build)?

Yes, with the latest release

### Screenshots showing the issue

no screenshots needed

### System information

- OS & OS version: Win 11
- DPI/HiDPI/scaling value, if not 100% (e.g. 125%, 150%...):
- Firefox version: 146.0.1
- Firefox theme (e.g. default, build in light/dark, external theme + link): Brushed Metal (Chrome) 2.0 (this is addon)

Reproduce the issue in Firefox 146.0.1 with the reported CustomCSSforFx settings and a middle-click on the tab bar. Compare behavior and available CSS changes between CustomCSSforFx 4.6.2 and 4.7.5; done means the middle mouse button opens a new tab with the latest release enabled.

Written by the indexing model from the issue text.