fixes possible crash if a processor modifies port-count
1. a processor is inserted and activated with processor-lock held
2. only after that the process_lock() is taken, configure_processors() is called which reconfigures-IO
BUT if the processor that is inserted changes the channel count AND audio is processed before IOs are reconfigured
-> possible crash (invalid port-buffers)
To reproduce: Bus1 (2in, 3out), Bus2 (2in, 3out)
- add a send from Bus1 to Bus2,
- then add a processor to Bus1, just before the send which
increases the channel-count to 4 -> occasional crash or assert.
7e3282486d