I can only assume this is a bug, but I can’t work out how to reliably reproduce it.
On occasion, after closing all tabs in a window, the window itself remains but is ‘stuck’
The usual window controls on the top left are disabled, none of the shortcut commands (e.g. CMD+W) respond, and the New Tab option (whilst still available in the menu) doesn’t have any effect either.
The window is completely non-responsive, it can be moved but not closed or resized. The only way to get rid of it is to quit Sublime Text and, when reopened, it is replaced with a normal working window.
Running Build 4126