core: in LoA case, add maintain curve to indication curve before finding intersection with overlay envelope

[Erashin]

Fixes #10443.

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.94%. Comparing base (4ddefb0) to head (d187915).
Report is 1 commits behind head on dev.

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Additional details and impacted files

@@           Coverage Diff           @@
##              dev   #10528   +/-   ##
=======================================
  Coverage   81.94%   81.94%           
=======================================
  Files        1076     1076           
  Lines      107583   107583           
  Branches      731      731           
=======================================
  Hits        88156    88156           
  Misses      19388    19388           
  Partials       39       39           

Flag	Coverage Δ
editoast	74.32% <ø> (ø)
front	89.46% <ø> (ø)
gateway	2.18% <ø> (ø)
osrdyne	3.28% <ø> (ø)
railjson_generator	87.50% <ø> (ø)
tests	88.14% <ø> (ø)

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[bougue-pe]

We really need some testing on those cases at some point (unit would be better, could be integration).
Anyway, this patch is fine 👍

[bougue-pe]

Thanks!
(You'll need to rebase after some other work on dev branch)