This cleans up some things I noticed when I implemented the mute flag handling. It removes the hack that manually forces flag 2 on all channels with number 9, regardless of the device.
I presume the hack was done for the earliest SCI 1 games, due to improper handling of flag 1.
Fixes access violation when playing sound 35 in early versions of SQ3.
This sound has the digital sample flag set but it doesn't contain any
digital sample data. Bug #13206