Immediate manager eats exceptions

[Alex Grönholm]

I forgot to set the author of the message, and I was left wondering why my message was never delivered despite not getting any errors with the immediate manager. Turns out there was an IndexError at message.py:112:

 return self.sender or self.author[0]

This exception was however silently discarded, which obviously should never happen. Instead, a friendly exception reminding me that at least one author must be set should've been raised (and delivered to my application!).

[Alice Zoë Bevan–McGregor]

What transport was in use? The immediate manager only explicitly handles three exceptions, none of which are IndexError.