saving causes tab gui mouse label to flash

Describe the bug
Triggering a write with unsaved buffers causes a label to flash when the mouse cursor is hovering over tabs.

If you have various kinds of autosave features enabled, as I do, this results in the mouse label flashing constantly during editing.

To Reproduce

1. /Applications/MacVim.app/Contents/bin/mvim --clean
2. :e 0.txt
3. :tabnew 1.txt
4. move mouse over the tab for 1.txt and ensure it is selected by clicking it
5. without moving the mouse, cause changes to 1.txt by entering insert mode o, typing asdfg, escaping <esc>, and saving :w<cr>
6. The gui label 1.txt flashes on the tab as the save completes. This is the informative label that describes the tab name on mouse hover.

Expected behavior
I would hope that the label would stay invisible.

Environment (please complete the following information):

• MacVim 8.2.3455, latest as of date
• OS: MacOS Big Sur 11.6

macOS 上で、記載されている :e、:tabnew、編集、:w のシーケンスを使い、/Applications/MacVim.app/Contents/bin/mvim --clean でフラッシュを再現してください。まず、保存中の MacVim のタブのマウスホバーラベル処理を追跡し、カーソルが選択されたタブ上に留まっているときにラベルが表示されないままであることを確認してください。