When de-selecting the last remaining category of an event and then trying to save, instead of saving, IncidenceEditor pops a dialog about some Akonadi exception.



Dialog 1: [incidencechanger.cpp:427 in akonadi-calendar]
Error while trying to modify calendar item. Error was: Akonadi::Exception: No objects specified
[OK]



Clicking OK leads to Dialog 2: [incidencedialog.cpp:490 in incidenceeditor]
Unable to store the incidence in the calendar. Try again?

Reason: Akonadi::Exception: No objects specified
[Yes] [No]



Yes loops back to dialog 1, No lets me control IncidenceDialog again, but without saving the item with no categories. A click on Abort in IncidenceDialog, and it asks me to discard changes. If I do, and reopen it for the same event, the category is still set.

Strangly, the issue does not occur on all my events, but on most. On some few, the dialog lets me remove all categories. I could not find any pattern, though.

Setting an arbitrary non-empty set of categories works for every event, only the empty set has this issue.

Version is 5.6.0, which is currently not in bugzilla (although underway).