Wrong X icon color in fullscreen dark mode

Bug report

• iTerm2 version: Build 3.5.0
• OS version: 14.5 (23F79)
• com.googlecode.iterm2.plist

PLEASE ATTACH YOUR PLIST FILE FOR BUG REPORTS! Seriously! I'll probably ask you for it if you don’t.

Detailed steps to reproduce the problem

1. Set mac theme (appearance) to Dark
2. Fullscreen iTerm2 (using the green button)
3. Hover over the top of the screen

What happened

The X for the (only) tab is dark on a dark background, and hard to see

It's also dark on dark for the selected tab when in fullscreen mode.

What should have happened

The X should be light (similar to how it is when you have multiple tabs in not fullscreen mode)

Or maybe it shouldn't be there at all (when you only have 1 tab)? Not sure what the point of it is since when you only have 1 tab, it closes the window when you try to close the one tab.

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