TrdPid Interpolate error spam fix #3067

Fixing spam of error messages "LitFindGlobalTracks spam: Error in TH2F::Interpolate: Cannot interpolate outside histogram domain." #3067

The errors are comming up for TrdHit EnergyLoss values = -1. (dedx = -1.).
This MR only removes the error spam, but not the underlying problem why there are dEdx values = -1.