MSO crash on Linux

[faultdiagnosistoolbox]

MSO crashes on Linux (but not on Mac) for the attached cases.

reported by Silke.

fdt_errors.zip

[faultdiagnosistoolbox]

A quick check gives that it seems to have something to do with non-used variables/equations. If I purge the model from such, it works, e.g. run a command

model.SubModel([], [], remove=True)