Source.add_line does not handle the types of masked values
When a first line is added to a source, if one of the values is masked, its type is set to STR_DTYPE because the type of a masked value is numpy.ma.core.MaskedConstant
:
https://git-cral.univ-lyon1.fr/MUSE/mpdaf/blob/master/lib/mpdaf/sdetect/source.py#L987-992
In addition to having the wrong type, if a format is passed to add_line (e.g. to format floats) this may raise a ValueError.