add explicit default initialization for flag in undo redo operation

core/object/undo_redo.h

@@ -58,7 +58,7 @@ private:
 			TYPE_REFERENCE
 		} type;
 
-		bool force_keep_in_merge_ends;
+		bool force_keep_in_merge_ends = false;
 		Ref<RefCounted> ref;
 		ObjectID object;
 		StringName name;