This block is inside if (m_currentOperation == OperationProcessiTIPMessage)
so this is the signal that the caller (SyncItipHandler in kdepim-addons) expects.
Whether one faulty calendar item should lead to a complete calendar loading
failure, a messagebox when accepting an invitation, and a failure to insert
the invitation into the calendar, is another debate (and another fix surely),
but at least the event loop in SyncItipHandler finishes on error too.