Fix remaining tab crash from not clearing tracking tags correctly

Similar to #1334. The old PSMTabBarControl code has a lot of dubious
straggling states regarding the tracking tags. Seems like previous macOS
versions tolerated that but in the newer macOS versions, the tags seem
to be reused for other purposes and so when you double-remove the tags,
you get into trouble.

Related to #1333

src/MacVim/PSMTabBarControl/source/PSMTabBarControl.m

@@ -476,9 +476,11 @@ - (void)removeTabForCell:(PSMTabBarCell *)cell
     [[NSNotificationCenter defaultCenter] removeObserver:cell];
     if([cell closeButtonTrackingTag] != 0){
         [self removeTrackingRect:[cell closeButtonTrackingTag]];
+        [cell setCloseButtonTrackingTag:0];
     }
     if([cell cellTrackingTag] != 0){
         [self removeTrackingRect:[cell cellTrackingTag]];
+        [cell setCellTrackingTag:0];
     }
 
     // pull from collection
@@ -665,9 +667,11 @@ - (void)update
         [[NSNotificationCenter defaultCenter] removeObserver:cell];
         if([cell closeButtonTrackingTag] != 0){
             [self removeTrackingRect:[cell closeButtonTrackingTag]];
+            [cell setCloseButtonTrackingTag:0];
         }
         if([cell cellTrackingTag] != 0){
             [self removeTrackingRect:[cell cellTrackingTag]];
+            [cell setCellTrackingTag:0];
         }
     }