WelcomePlugin: java script fix

missing var

Change-Id: I3bce04272285c07c545fee3d5f1a8f0c898abdb7
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@nokia.com>

share/qtcreator/welcomescreen/widgets/ToolTip.qml

@@ -76,7 +76,7 @@ Item {
 
     function hide() {
         toolTip.opacity = 0;
-        oldClip = originalParent.clip
+        var oldClip = originalParent.clip
         originalParent.clip = false
         toolTip.parent = originalParent
         originalParent.clip = true