window-actor: Another simple clang warning fix

If we explicitly check for a NULL pointer, clang will assume
that the pointer may be NULL at some point. We clearly rely
on the pointer being non-NULL earlier, so fix this guy up.

https://bugzilla.gnome.org/show_bug.cgi?id=674876

src/compositor/meta-window-actor.c

@@ -745,11 +745,8 @@ meta_window_actor_has_shadow (MetaWindowActor *self)
    * Always put a shadow around windows with a frame - This should override
    * the restriction about not putting a shadow around ARGB windows.
    */
-  if (priv->window)
-    {
   if (meta_window_get_frame (priv->window))
     return TRUE;
-    }
 
   /*
    * Do not add shadows to ARGB windows; eventually we should generate a