Hessian calculation with non-equilibrium geometry crashes instead of printing a warning

[ppinski-hqs]

Describe the bug
Attempting to calculate the Hessian of a non-equilibrium geometry with GFN-FF (without --strict option) causes an error instead of a warning.

To Reproduce
Steps to reproduce the behavior (files inside the attached archive c2h4.zip:

1. happens with attached input file c2h4.xyz
2. start xtb (binary release version 6.7.0) with: xtb c2h4.xyz --hess --gfnff --verbose >stdout 2>stderr
3. run xtb
4. output inside the attached archive, files stdout and stderr

Expected behaviour
I would expect the Hessian to be calculated for the non-equilibrium geometry, maybe with a warning, but without crashing.

Additional context
Without the --gfnff flag (that is with GFN2-xTB), a warning about an incompletely optimized geometry appears, but the Hessian is calculated nonetheless.

[ppinski-hqs]

This seems to be a special case of issue #1054, so closing this issue for now.