Fixed empty if statement in QWindow.cpp

Change-Id: Ib324eb30da1e16f01b9655ed293244fb50b621b8
Reviewed-on: http://codereview.qt.nokia.com/3289
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

src/gui/kernel/qwindow.cpp

@@ -574,7 +574,7 @@ bool QWindow::event(QEvent *event)
         Q_D(QWindow);
         bool wasVisible = visible();
         destroy();
-        if (wasVisible);
+        if (wasVisible)
             d->maybeQuitOnLastWindowClosed();
         break; }