SCUMM: ZAK: No bus engine sound on C64

[GermanTribun]

ScummVM: Newest Snapshot
Game: Zak
Version: C64

I noticed that in a different report, but to do it the correct way, here the observation.

Normally, after paying in the bus, the door should close and you should hear an engine sound before the scene changes (and the sound does fade out on the next scene). Unlike in other ports, the engine sound however is missing on the C64, though it is there when playing emulated.

Thus the sound effect for some reason is not called in ScummVM.

In the following video played on an emulator, you can hear the sound of the bus at 7:18. ​https://www.youtube.com/watch?v=6-dwcapMVO8