Invalid use of NULL references

Original summary: Increased testing failures with Clang 3.4 and later

With newer versions of Clang, the number of bad and failed tests has increased severely. Lots of SIGILLs and SIGFPEs. At least part of the problem is using NULL as a reference (C++ does not allow NULL references), e.g.

inline TColStd_Array1OfReal& BSplCLib::NoWeights()
{
  return (*((TColStd_Array1OfReal*) NULL));
}

Here is a possibly complete list of instances where this occurs:

src/BRep/BRep_CurveRepresentation.cxx:186: return *((Handle(Geom_Curve)*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:211: return *((Handle(Geom_Surface)*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:223: return *((Handle(Geom2d_Curve)*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:234: return *((Handle(Geom2d_Curve)*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:266: return *((GeomAbs_Shape*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:288: return *((Handle(Geom_Surface)*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:300: return *((TopLoc_Location*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:313: return *((Handle(Poly_Polygon3D)*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:335: return *((Handle(Poly_Polygon2D)*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:357: return *((Handle(Poly_PolygonOnTriangulation)*) NULL);
src/BRep/BRep_CurveRepresentation.cxx:393: return *(Handle(Poly_PolygonOnTriangulation)*)NULL;
src/BRep/BRep_CurveRepresentation.cxx:404: return *(Handle(Poly_Triangulation)*)NULL;
src/BRep/BRep_CurveRepresentation.cxx:417: return *((Handle(Poly_Polygon2D)*) NULL);
src/BRep/BRep_PointRepresentation.cxx:136: return *((Handle(Geom_Curve)*) NULL);
src/BRep/BRep_PointRepresentation.cxx:159: return *((Handle(Geom2d_Curve)*) NULL);
src/BRep/BRep_PointRepresentation.cxx:182: return *((Handle(Geom_Surface)*) NULL);
src/BSplCLib/BSplCLib.lxx:38: return (*((TColStd_Array1OfReal*) NULL));
src/BSplCLib/BSplCLib.lxx:48: return (*((TColStd_Array1OfInteger*) NULL));
src/BSplSLib/BSplSLib.lxx:100: return (*((TColStd_Array2OfReal*) NULL));
src/Expr/Expr_BinaryExpression.cxx:77: return *( ( Handle_Expr_GeneralExpression* )NULL );
src/NCollection/NCollection_DoubleMap.hxx:133: return * (TheKey2Type *) NULL; // For compiler
src/NCollection/NCollection_IndexedMap.hxx:123: return * (TheKeyType *) NULL; // This for compiler
src/NCollection/NCollection_Map.hxx:113: return * (TheKeyType *) NULL; // For compiler
src/PLib/PLib.lxx:19: return (*((TColStd_Array1OfReal*) NULL ));
src/PLib/PLib.lxx:24: return (*((TColStd_Array2OfReal*) NULL ));