Fix ARMATURE_OT_layers_show_all now works with COW

source/blender/editors/armature/pose_edit.c

@@ -819,6 +819,7 @@ static int pose_armature_layers_showall_exec(bContext *C, wmOperator *op)
 	
 	/* note, notifier might evolve */
 	WM_event_add_notifier(C, NC_OBJECT | ND_POSE, ob);
+	DEG_id_tag_update(&arm->id, DEG_TAG_COPY_ON_WRITE);
 	
 	/* done */
 	return OPERATOR_FINISHED;