Fix leak in QNSView.

Change-Id: Ide0e826bf068340c86d87a8ccbb3bd58b60f6d8c
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>

src/plugins/platforms/cocoa/qnsview.mm

@@ -113,6 +113,8 @@ static QTouchDevice *touchDevice = 0;
              name:NSViewGlobalFrameDidChangeNotification
              object:self];
 }
+    delete currentCustomDragTypes;
+
     [super dealloc];
 }