[BUG] Average structure job for simulation without a unit cell

[ChiCheng45]

Description of the error
The average structure job fails for a simulation without a unit cell. Some failures are expected, for example, when you don't have a unit cell and select the .cif output. In some cases it fails for something that it should work for, for example, .xyz outputs.

The average structure job should work with .xyz and other related output file formats for simulations without a unit cell. Maybe the output file should be restricted e.g. for simulations without a unit cell the .cif output file shouldn't be available. Also, the job appears to do a lot of the calculation before failing, It should do the unit cell check and fail early.