Add error message when fitting with empty metadata

[fealho]

CU-86b54q0kz, Resolve #2553.

[sdv-team]

Task linked: CU-86b54q0kz SDV - Metadata validation should error if metadata is empty #2553

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.07%. Comparing base (647b5c9) to head (62b072f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2632      +/-   ##
==========================================
- Coverage   98.08%   98.07%   -0.02%     
==========================================
  Files          70       70              
  Lines        7416     7419       +3     
==========================================
+ Hits         7274     7276       +2     
- Misses        142      143       +1     

Flag	Coverage Δ
integration	75.92% <100.00%> (-0.17%)	⬇️
unit	96.84% <66.66%> (-0.02%)	⬇️

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