Loading scores for the measure commands fails on non-float scores

src/bob/bio/base/score/load.py#L663 and src/bob/bio/base/score/load.py#L650 cast a CSV score column to float, but it could contain other things (nothing or None) that cannot be converted to float. This needs to be handled correctly.

Possible solution:

• Convert all non-float values to float("nan"), this should be handled correctly by the measure commands.