bugfix: work on a copy of the object list to prevent error

hiding/unhinding while interating on objects can void an object, giving back None), because Blender's cached object list is invalidated

fn.py

@@ -805,9 +805,11 @@ def apply_collection_states(collection, context=None):
         return ({'WARNING'}, f"No stored state for '{key}'")
         # return {'CANCELLED'}
 
+    ## Collect objects before changing visibility (can invalidate all_objects cache)
+    all_objects = {o.name: o for o in collection.all_objects}
     for obj_name, obj_state in state['objects'].items():
         # obj = context.scene.objects.get(obj_name)
-        obj = collection.all_objects.get(obj_name)
+        obj = all_objects.get(obj_name)
         if obj:
             obj.hide_viewport = obj_state.get('hide_viewport', False)
             obj.hide_render = obj_state.get('hide_render', False)