Add check in job.ini for scenario calculations

[CatalinaYepes]

If the user does not provide gsim or gmlt in a scenario calculation, the following error message appears:

  File "/Users/cye/oq319/lib/python3.11/site-packages/openquake/calculators/event_based.py", line 229, in gen_event_based
    yield event_based(proxies, cmaker, stations, dstore, monitor)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/cye/oq319/lib/python3.11/site-packages/openquake/calculators/event_based.py", line 284, in event_based
    mean_stds = cmaker.get_mean_stds(
                ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/cye/oq319/lib/python3.11/site-packages/openquake/hazardlib/contexts.py", line 1253, in get_mean_stds
    raise ValueError('Total StdDev is zero for %s' % gsim)
ValueError: Total StdDev is zero for [FromFile]

The check should be done at the beginning of the calculation. To replicate the error, comment gsim line in any demo calculation for scenarios.