NSTrackingSeparatorToolbarItem causes white bar over top of content in macOS 27 developer beta 5

macOS 27 developer beta 5 (26A5406e) introduces a bug that causes a white bar to appear over window content if the window’s toolbar has an NSTrackingSeparatorToolbarItem. I filed FB24266969 with Apple describing this. I have a sample project demonstrating this. This is a screenshot of the result: To reproduce the issue: Open the attached sample project. Observe that the app presents a simple…