[Trunk] Undoing clef change at start of bar does not affect grace notes (apparently)

Tested with 2.0.0 prerelease r4847 on Win7 x64.

When grace notes appear on a bar, and the clef is changed subsequently, then the grace notes are moved accordingly. When undoing this change (CTRL-Z or "Edit"→"Undo"), the clef and notes revert to before the clef change, but the grace notes remain at the place where they were after the clef change.

Before clef change:

Clef change:

After undoing clef change:

What is weird, is that when you drop another clef on top of the first clef, the grace notes are again placed correctly according to the replacement clef. So it looks like a screen refresh issue.