Patch for bug reported in AGENE-1952 when using for_reweighting 1 in PowhegControl
requested to merge atlas-physics/pmg/mcexperts/powheg-experts/athena:dev-21.6-PwC-FixXWGTUP-Patch into 21.6
This fixes a bug reported by @amoroso affecting 21.6.53 and 21.6.54 (but probably also older releases), when using for_reweighting 1 in PowhegControl. More details about the bug can be found in the AGENE-1952 ticket.