Steps:

1. Create a recuring event starting on monday, daily for 6 times.
2. Select the occurrence on Friday and delete it (only this occurrence)
3. Edit Tuesdays event, change subject and choose to apply changes to ALL events in a series.

Result: Friday's occurence reappears.
Expected: Friday's occurence is still invisible.

Note: There will be no issue if in point 3 you edit the first event in a series.