Fix SAPI4 (#18262)
Fixes #18259.
Summary of the issue:
Digalo 2000 voices (SAPI4) do not work and cause memory access violation errors.
Description of user facing changes:
The issue should be fixed.
Description of developer facing changes:
None.
Description of development approach:
For some reason, the IAudio object was destroyed before it was even being used, causing its COM pointers to be reset to zero and access violations afterwards. So code are added to guard the SAPI4 IAudio object from being released prematurely.
Prevent joining the audio thread if the audio object is destroyed before starting.
