user configuration errors should be papered over

Reported by @albertotirla

Steps to reproduce

Not sure how, just reporting here what was said on matrix.

Obtained behavior

“when the tinyest thing is wrong in sd's configuration, it doesn't just remove that module with a warning, fallback to defaults, any of that, but instead it entirely crashes, leaving the user with absolutely no speech”

Expected behavior

spd should always at least produce speech, whatever configuration error the user may have done.

Of course, it the user directed speech to an audio card whose headphones are not connected, spd can't do much, but there are probably various situations where spd detects an error, and should be able to fallback on something that works.