Qt4: Always parent all preferences to avoid funny windows/widget effects.

(cherry picked from commit 9747e574)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/components/complete_preferences.cpp

@@ -472,10 +472,10 @@ AdvPrefsPanel::AdvPrefsPanel( intf_thread_t *_p_intf, QWidget *_parent,
         ConfigControl *control;
         if( ! box )
             control = ConfigControl::createControl( VLC_OBJECT( p_intf ),
-                                        p_item, NULL, layout, i_line );
+                                        p_item, this, layout, i_line );
         else
             control = ConfigControl::createControl( VLC_OBJECT( p_intf ),
-                                    p_item, NULL, boxlayout, i_boxline );
+                                    p_item, this, boxlayout, i_boxline );
         if( !control )
             continue;