Edge issue in spline computed by GMCJDriver::BootstrapXSecSplineSummation()

[candreop]

Reported by @Igor144 in GENIE docdb 297.

Issue is connected to the energy range for the spline representing the sum of all x-section splines, computed by GMCJDriver::BootstrapXSecSplineSummation().

@Igor144 says that "If the user calculates the spline till 200 GeV then max will be equal to 220 GeV. Since there is no precalculated values in the range 200–220 GeV the method void GEVGDriver::CreateXSecSumSpline sets them equal to zero, which leads to wobble of the spline close to the right end"