Make sure that mousing over Chrome "internal div" doesn't trigger a mouseleave. Fixes #8209.

Follow up to 4a828c93d4
which was stupid and got reversed.

src/event.js

@@ -653,6 +653,12 @@ var withinElement = function( event ) {
 	// Firefox sometimes assigns relatedTarget a XUL element
 	// which we cannot access the parentNode property of
 	try {
+
+		// Chrome does something similar, the parentNode property
+		// can be accessed but is null.
+		if ( parent !== document && !parent.parentNode ) {
+			return;
+		}
 		// Traverse up the tree
 		while ( parent && parent !== this ) {
 			parent = parent.parentNode;