Fix cluster count offsets
This MR fixes the scifi cluster count offset calculation, in order to have proper offsets for all events, independently of the event mask.
This was causing a crash in sequences where the SciFi decoding is inside and event mask, due to the logic here that requires defined offsets for all events.
This should fix the issue observed when running hlt1_pp_forward_then_matching_no_ut_no_lumi
observed by @kaaricha
Edited by Christina Agapopoulou