[RM-8454] Segmentation fault when launching amazed with an existing empty calibration dir

Created on 2023-10-31 16:37:39 by Fanny Dufresne. % Done: 100

When launching amazed with :

• an non-existent calibration_dir in config.json: an error is raised.
• an existing calibration_dir directory but which doesn't contain the expected calibration files: a segmentation fault error with no more comments

=> We would like a more explicit error if calibration_dir does not contain the expected files

MR: https://gitlab.lam.fr/CPF/cpf-redshift/-/merge_requests/562