[client] chore(merge): add null checks for backwards compatibilty (#243)

[antoinemzs]

Close #243

[guzmud]

LGTM

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 70.34%. Comparing base (4b32065) to head (40a738b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pyoaev/configuration/sources.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #244      +/-   ##
==========================================
- Coverage   70.36%   70.34%   -0.03%     
==========================================
  Files          49       49              
  Lines        1964     1966       +2     
==========================================
+ Hits         1382     1383       +1     
- Misses        582      583       +1     

Flag	Coverage Δ
connectors	70.34% <75.00%> (-0.03%)	⬇️

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