1.18.00.00 MPT might crash after deleting instruments

[Saga Musix]

Full Version:
OpenMPT v1.18.00.00 (and most likely earlier)

Has the bug occured in previous versions? If yes, please specify version(s): (This option is optional, and doesn't need research. But in case you know...)
Not tested, but it's likely.

Edit: Bug confirmed, fix is on its way

Description of the bug:
OpenMPT will crash when (auto)saving a MPTM file after deleting instruments from the treeview due to a missing null pointer check.

Until there's fix is available, don't delete instruments from the treeview if you're working in MPTM format. Actually, deleting the last instrument is okay, but any other instruments will crash OpenMPT the next time you're going to save the module.

Edit: A similar bug was found, concerning all modules with instruments. Deleting an instrument and then converting the module to another format with instrument support can also crash OpenMPT.