Bug: Fatras sets step size to 0 #2543
Description
In #2532 I tried to introduce an assert in the ConstrainedStep to check for 0 step size. This seems to happen in Fatras with secondary particles. I guess they are created on a material layer and the propagation is then started without a starting surface which results in resolving the layer which is then at distance 0.
The solution to this might be to add the surface to the particle state in Fatras so the propagation can continue where it left of.