Merge branch 'heal_without_face_colours' into 'master'

Allow OCCGeometry.Heal without face_colours (if built in py)

See merge request jschoeberl/netgen!435

libsrc/occ/occgeom.cpp

@@ -411,6 +411,7 @@ namespace netgen
             // Set the original colour of the face to the newly created 
             // face (after the healing process)
             face = TopoDS::Face (exp0.Current());
+            if(face_colours)
               face_colours->SetColor(face,face_colour,XCAFDoc_ColorSurf);
          }
          shape = rebuild->Apply(shape);