Crash when Deep Cloning FDS instruments

[Nyde42]

When I Deep Clone an FDS instrument, 0CC-Famitracker crashes. However, the deep cloning seems to work anyways, since the recover.ftm that is created does have the deep cloned instrument and everything works as if there was no issue at all. The crash results in the following MiniDump:

I assume the problem is that Deep Cloning tries to find the next empty envelope sequence, but FDS instruments each have unique envelopes and therefore don't have them indexed the same way that most other instruments do?