for (; aItLPB.More(); aItLPB.Next()) {
const Handle(BOPDS_PaveBlock)& aPB=aItLPB.Value();
nE=aPB->Edge();
+ if (nE < 0) {
+ continue;
+ }
const TopoDS_Edge& aE=(*(TopoDS_Edge *)(&myDS->Shape(nE)));
aC2D=BRep_Tool::CurveOnSurface(aE, aDF, aT1, aT2);
if (aC2D.IsNull()) {