The msrp_notify() and mvrp_notify() functions call dispatch table
notify callbacks without checking for NULL. In MSRP, the
TALKER_FAILED attribute type has a NULL notify callback, which would
crash if a talker-failed attribute received a registrar state change
notification (e.g. RX_NEW triggering NOTIFY_NEW).
Add NULL checks before calling the dispatch notify callbacks, matching
the defensive pattern used in the encode path.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add in input/output stream, setup the talker/listeners.
Implement IEC61883 audio packets, send and receive data.
Implement talker encoding.
With this, audio can be sent and received from MOTU M64.
