Make QC fail upon error parsing dataset

https://github.com/MetOffice/CDDS/blob/a8b74e554d307965b0f93e31b3b3e7a251498d02/cdds/cdds/qc/dataset/cmip7.py#L144-L145

When QC experiences an error parsing a dataset (i.e. there is a missing attribute that causes a failure to aggregate files), functionality should be put in place so that QC fails rather than silently continuing. This will avoid issues with empty approved variable lists being parsed to transfer which then fails causing misleading error messages.

Start at cdds/cdds/qc/dataset/cmip7.py lines 144-145 and inspect how dataset parsing errors are handled during file aggregation. Make QC fail when a missing attribute causes parsing to error, rather than continuing with an empty approved variable list; done means the misleading transfer failure is avoided.

Written by the indexing model from the issue text.