InstrumentSoundShaping: more sanity checking
InstrumentTrack: partly revert ad27039b9bbba2ab1095ddd3c163a20a02956c96

Even though there are probably not many old projects out there, at least
old presets didn't load properly anymore as of ad27039b9bbba2ab1095ddd3.
Fix this by reintroducing compat code.