1. Connect to DB.
2. Rightclick some table and choose "View Data...".
3. Select some record and press "Delete Selected Record(s)" button.
4. Press "No" button in appeared dialog
Result: Button "Delete Selected Record(s)" becomes disabled, but record is still selected and can be deleted.
Workaround: select another record and select necessary record again.
But workaround is very inconvenient.
*** This issue has been marked as a duplicate of 154604 ***