Fixing recursion issue in TruthDecayCollectionMaker

Under certain circumstances, some decays will be created with loops in the particle records in the decays of BSM particles. It's a bit unusual, but when that happens there can be an infinite recursion induced in the truth decay collection maker, because the unique ID (previously: barcode) isn't set until after the decay vertex and outgoing particles are added to the record. That means if for some reason we have a vertex that loops back on itself, the particle could be added recursively and infinitely... until we get a stack overflow and crash (thanks to @amete for the tip there). Reported by @labruce . Should be fixed with this MR.