Bug 331221

I have an ownCloud server where all my calendar entries are stored. This calendar is synchronized on both the Android smartphone and via Akonadi. This ownCloud instance also contains a second calendar, which I import from Outlook on a regular basis  (via cron job). In this case, I have to drop the old calendar database and re-import the complete calendar from outlook again, to prevent duplicate items. After the import, the following error message appears (160 Popup Messages!):

"Error while trying to delete calendar item. Error was: No items found"

If the database is not deleted (which generates duplicate items), no error message appears.

Reproducible: Always

Steps to Reproduce:
1. Sync calendar via caldav
2. Delete all existing calendar items on server and re-import all entries again (also the new onces)
3. Sync again => crash
Actual Results:  
160 Popup Messages:
"Error while trying to delete calendar item. Error was: No items found"

Expected Results:  
Same like Android:
Refresh the calendar without error messages.