core: we sometimes fail to find a block path from a route

[eckter]

What happened?

This assertion sometimes fail, only on an imported infra (France): assert(blockPaths.isNotEmpty()). The route path may contain a single route.

This can happen in both STDCM and standalone sim.

What did you expect to happen?

No response

How can we reproduce it (as minimally and precisely as possible)?

The most straightforward way to reproduce it is to iterate over the routes in the infra and trying to convert them to block paths

What operating system, browser and environment are you using?

• Env: Local

OSRD version (top right corner Account button > Informations)

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