Fix nullptr deref in QMenu::mouseReleaseEvent()

879eb2c introduced a nulltr deref.
Amend the patch to fix it.

Coverity-Id: 896788
Change-Id: Ic05db9f5bfb67ece01a0e030400697d97712646e
Reviewed-by: Marc Mutz <[email protected]>
(cherry picked from commit 8e89eef)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

Author: ASpoerl

src/widgets/widgets/qmenu.cpp

@@ -2945,7 +2945,7 @@ void QMenu::mouseReleaseEvent(QMouseEvent *e)
 #endif
                 d->activateAction(action, QAction::Trigger);
         }
-    } else if ((!action || action->isEnabled()) && !action->isSeparator()) {
+    } else if (!action || (action->isEnabled() && !action->isSeparator())) {
         d->hideUpToMenuBar();
     }
 }