Clip editor: Fix missing frame update on undo

It is possible that undo will change current scene frame and that was
not synchronizing current frame from scene to movie clip user.

Reported as a part of T66519.

Reviewers: brecht

Reviewed By: brecht

Maniphest Tasks: T66519

Differential Revision: https://developer.blender.org/D5280

source/blender/editors/space_clip/space_clip.c

@@ -420,6 +420,14 @@ static void clip_listener(wmWindow *UNUSED(win), ScrArea *sa, wmNotifier *wmn, S
         ED_area_tag_redraw(sa);
       }
       break;
+    case NC_WM:
+      switch (wmn->data) {
+        case ND_FILEREAD:
+        case ND_UNDO:
+          clip_area_sync_frame_from_scene(sa, scene);
+          break;
+      }
+      break;
   }
 }