Nef_3: Use the skipVEL parameter to ensure result is always an SFace

[GilesBathgate]

Summary of Changes

This sets the skipVEL (Skip SVertices SEdges and SLoops) parameter to true, when calling the locate method in get_visible_facet of SNC_const_decorator. Since it's trying to locate an Sface, it makes no sense for locate to match SVertices, SEdges or SLoops, and if it does the assertion in get_visible_facet will fail.

Release Management

• Affected package(s): Nef_3
• Issue(s) solved (if any): Nef_3: it is not possible to decide which one is a visible facet (if any) assertion error #7271
• Feature/Small Feature (if any): bugfix
• License and copyright ownership: CGAL authors

[GilesBathgate]

As was previously stated:

In commit ebd5e00 the value of true was passed to L.locate() which skips needless tests.
Applying the same change to the get_visible_facet method of SNC_const_decorator makes the assertion exception never occur.
@afabri However I am not sure if it would be correct to apply the same change here or not.