Fix editors potentially being used twice

editor/editor_node.cpp

@@ -2096,14 +2096,25 @@ void EditorNode::edit_item(Object *p_object, Object *p_editing_owner) {
 	if (!item_plugins.is_empty()) {
 		ObjectID owner_id = p_editing_owner->get_instance_id();
 
+		List<EditorPlugin *> to_remove;
 		for (EditorPlugin *plugin : active_plugins[owner_id]) {
 			if (!item_plugins.has(plugin)) {
+				// Remove plugins no longer used by this editing owner.
+				to_remove.push_back(plugin);
 				plugin->make_visible(false);
 				plugin->edit(nullptr);
 			}
 		}
 
+		for (EditorPlugin *plugin : to_remove) {
+			active_plugins[owner_id].erase(plugin);
+		}
+
 		for (EditorPlugin *plugin : item_plugins) {
+			if (active_plugins[owner_id].has(plugin)) {
+				continue;
+			}
+
 			for (KeyValue<ObjectID, HashSet<EditorPlugin *>> &kv : active_plugins) {
 				if (kv.key != owner_id) {
 					EditorPropertyResource *epres = Object::cast_to<EditorPropertyResource>(ObjectDB::get_instance(kv.key));