0031430: Offset surfaces on C1 surfaces (with multiplicity equal to degree) may still...

0031430: Offset surfaces on C1 surfaces (with multiplicity equal to degree) may still throw exception

In constructor of Geom_RectangularTrimmedSurface, skip check if an offset surface has insufficient continuity. The reason is that this surface has already passed the check once created. So, here we must not apply more strict check than that first time.