Don't access elements in the vector by adding an int to an iterator (see ATLASRECTS-6349)
A non-reproducible FPE is observed at this line (see ATLASRECTS-6349), presumably because it is accessing garbage rather than an element of the vector. Switching to vector.at(nextSf) might not solve the problem, but should at least make it clearer what the problem is by giving an exception more directly related to the issue. RunTier0Tests.py confirms no differences from this change.
Edited by Christos Anastopoulos