Fix rs.to_dict(orient='uuids') in the case that rs.group is None

[AlexDo1]

I just stumbled upon an error in #296.

Old code produced an error, as rs.group just returns None when no group is associated to the ImmutableResultSet:

return {member.uuid: member.to_dict() for member in [rs.group, *rs._members]}

New code checks if member has attribute to_dict before adding it to returned dictionary:

return {member.uuid: member.to_dict() for member in [rs.group, *rs._members] if hasattr(member, 'to_dict')}

[codecov[bot]]

Codecov Report

Merging #298 (23db118) into main (4c57796) will increase coverage by 0.01%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #298      +/-   ##
==========================================
+ Coverage   64.48%   64.50%   +0.01%     
==========================================
  Files          75       75              
  Lines        3934     3922      -12     
==========================================
- Hits         2537     2530       -7     
+ Misses       1397     1392       -5     

Flag	Coverage Δ
e2e	64.50% <0.00%> (+0.01%)	:arrow_up:

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Impacted Files	Coverage Δ
metacatalog/util/results.py	74.58% <0.00%> (ø)

... and 1 file with indirect coverage changes