Fix opening a tab crashing MacVim

This seems to be a really old bug but new interactions with macOS
(probably due to macOS 13 Ventura) caused it to surface and crash.
Previously it was assuming a call to removeTrackingRect must always come
only after addTrackingRect was called, which was not a good assumption
to make. As a result, we could call this and end up triggering other
code in macOS when passing in a 0 tracking tag.

Fix #1333

src/MacVim/PSMTabBarControl/source/PSMRolloverButton.m

@@ -52,7 +52,9 @@
 
 - (void)removeTrackingRect
 {
-    [self removeTrackingRect:_myTrackingRectTag];
+    if (_myTrackingRectTag != 0)
+        [self removeTrackingRect:_myTrackingRectTag];
+    _myTrackingRectTag = 0;
 }
 
 // override for rollover effect