[gtk/gtk-4-6] actionmuxer: check for observer before unregistering

[Matthias Clasen <matthiasc src gnome org>]

commit 6d95ac92994f8c7562a43842cdd37bc261d40bf1
Author: Christian Hergert <chergert redhat com>
Date:   Mon May 2 15:33:34 2022 -0700

    actionmuxer: check for observer before unregistering
    
    This can happen if the group can be resolved even when doing the initial
    registration of an action as observer will not yet be in the GSList of
    watchers (and therefore has no weak references).
    
    Fixes a warning like the following:
    
     g_object_weak_unref: couldn't find weak ref

 gtk/gtkactionmuxer.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)
---
diff --git a/gtk/gtkactionmuxer.c b/gtk/gtkactionmuxer.c
index 60ee06dc58..94f734ca91 100644
--- a/gtk/gtkactionmuxer.c
+++ b/gtk/gtkactionmuxer.c
@@ -991,13 +991,15 @@ gtk_action_muxer_unregister_observer (GtkActionObservable *observable,
                                       GtkActionObserver   *observer)
 {
   GtkActionMuxer *muxer = GTK_ACTION_MUXER (observable);
-  Action *action;
+  Action *action = find_observers (muxer, name);
 
-  action = find_observers (muxer, name);
   if (action)
     {
-      g_object_weak_unref (G_OBJECT (observer), gtk_action_muxer_weak_notify, action);
-      gtk_action_muxer_unregister_internal (action, observer);
+      if (g_slist_find (action->watchers, observer) != NULL)
+        {
+          g_object_weak_unref (G_OBJECT (observer), gtk_action_muxer_weak_notify, action);
+          gtk_action_muxer_unregister_internal (action, observer);
+        }
     }
 }