rebdsimCombine - warning when merging simple histograms

[Laurie Nevay]

We get the following warning when merging simple histograms…

Found histogram> Event/SimpleHistograms/Stage1_FoM_+13_before_XY_per_5cm
Warning in <TH2D::Sumw2>: Sum of squares of weights structure already created
Found histogram> Event/SimpleHistograms/Stage1_FoM_+13_after_XY_per_5cm
Warning in <TH2D::Sumw2>: Sum of squares of weights structure already created

Confirmed other people than me see it.