Previously when the master-bus had more outputs than inputs,
Ardour crashed when the monitor-section was set up.
Removing a master-bus output port calls
Route::output_change_handler (master-bus)
-> Session::reset_monitor_section
which first removes the corresponding monitor-section input,
then output port. The latter triggers
ARDOUR::Route::output_change_handler (monitor-bus).
All with the process-lock held, so at this point in time Ardour
has removed the port-reference but the port still exists in the
backend.
Now the monitor-bus processors are re-configured and
the channel-count is updated. The port that was just removed
and triggered the ::output_change_handler() callback is
re-created.
unable to create port 'Monitor/audio_out 2': failed constructor
This fix changes the monitor-section to use strict-i/o (for plugins)
and also use master-bus output (not input) when configuring
processors.
aa69fe49f5