qt4: Use playlist_CurrentInput().

Should fix a race condition about freed input usage.

modules/gui/qt4/input_manager.cpp

@@ -590,8 +590,9 @@ void MainInputManager::customEvent( QEvent *event )
     {
         /* we are working as a dialogs provider */
         playlist_t *p_playlist = pl_Yield( p_intf );
-        p_input = p_playlist->p_input;
+        p_input = playlist_CurrentInput( p_playlist );
         emit inputChanged( p_input );
+        vlc_object_release( p_input );
     }
 }