FutureGammaPi0XGBoostTool: do not use invalid CaloCellID
do not lookup digits with invalid CaloCellID.
Must be applied in conjunction with LHCb!2546 (merged).
Sits on top of !2050 (merged), and is required for LHCb!2546 (merged), which does not support lookups with invalid CaloCellID
Edited by Rosen Matev