The root problem here is that with the original error handling a NULL
dereference occurs (IWineD3DBaseTexture_GetType()) when either the source or
destination texture is NULL. Rewriting the error handling changes the
indentation of almost the entire function though, so this patch ends up
rewriting the entire function.

mciwave: Simplify async command management by directly calling the right function instead of going through winmm again.