Only use default occurrence_url if no other definition is given. Also fix typo.
Only use default occurrence_url if no other definition is given. Also fix typo.

ic-labs/icekit-events,ic-labs/django-icekit,ic-labs/django-icekit,ic-labs/icekit-events,ic-labs/django-icekit,ic-labs/django-icekit,ic-labs/icekit-events