Default synthesizer settings not applied to new or loaded score

This is apparent in 3.1 beta, latest master.

Reproduce:

1. change the synth settings to use Velocity Only in the dynamics tab
2. click Set as Default
3. load any score, or create a new score, in which there are single-note-dynamics-enabled instruments.
4. the patches are switched to expressive ones instead of being left at the non-expressive ones

This shows that the default synth state is not being set on score creation or load.