Fix recursion issue in InDetSecVertexValidation
Sometimes (rarely) decays will be created with loops in the particle records in the decays of BSM particles, and when that occurs, descendent particles can be added recursively an infinite amount of times, leading to a stack overflow and crash. This is a MR to fix that case in InDetSecVertexTruthMatchTool:countReconstructibleDescendentPartitcles
Edited by Laura Elaine Bruce