front: editor - avoid API calls when no infra is selected

[sim51]

fix #6733

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 27.93%. Comparing base (7da176a) to head (5aa11cc).
Report is 2 commits behind head on dev.

Files	Patch %	Lines
...src/applications/editor/components/LayersModal.tsx	0.00%	5 Missing ⚠️
front/src/applications/editor/Map.tsx	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##                dev    #6734   +/-   ##
=========================================
  Coverage     27.92%   27.93%           
  Complexity     2172     2172           
=========================================
  Files          1041     1041           
  Lines        128654   128655    +1     
  Branches       2567     2567           
=========================================
+ Hits          35926    35934    +8     
+ Misses        91245    91238    -7     
  Partials       1483     1483           

Flag	Coverage Δ
core	79.36% <ø> (ø)
editoast	75.38% <ø> (-0.01%)	⬇️
front	8.41% <0.00%> (-0.01%)	⬇️
gateway	2.50% <ø> (ø)
railjson_generator	87.26% <ø> (ø)
tests	83.07% <ø> (+1.12%)	⬆️

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