QCocoaMenu: Fix crash with 10.7 QFileDialog shortcuts

Set target and action in menuHasKeyEquivalent in order to match
the specification, and to avoid QFileDialog crashes on OSX 10.7.

Task-number: QTBUG-17291
Change-Id: Ie8f88cbda31a42c3e1acd8d4ad36d54a295eac65
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>

src/plugins/platforms/cocoa/qcocoamenu.mm

@@ -163,6 +163,8 @@ QT_NAMESPACE_ALIAS_OBJC_CLASS(QCocoaMenuDelegate);
             // Whatever the current first responder is, let's give it a chance
             // and do not touch the Qt's focusObject (which is different from some native view
             // having a focus inside NSSave/OpenPanel.
+            *target = nil;
+            *action = menuItem.action;
             return YES;
         }