fix halfedge status for opposite edges when removing border degenerate faces

Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/remesh_impl.h

@@ -1699,6 +1699,10 @@ private:
       {
         set_status(hf, MESH_BORDER); //only 1 or 2 of the listed halfedges
                                      //will survive face removal, but status will be correct
+
+        halfedge_descriptor hfo = opposite(hf, mesh_);
+        if(status(hfo) != MESH_BORDER)
+          set_status(hfo, PATCH_BORDER);
       }
       CGAL::Euler::remove_face(h, mesh_);
     }