Fix edge case bug in flaggedrevs task
Fix edge case bug in flaggedrevs task

Sometimes, we don't get a dict back, but a list if the result is
empty (e.g. only log events).

Change-Id: I3b64972247bcac4fba00a08352d710739f66a9ca

wikimedia/labs-tools-crosswatch,wikimedia/labs-tools-crosswatch,wikimedia/labs-tools-crosswatch,wikimedia/labs-tools-crosswatch