check if is_collapse_ok before collapsing an edge of a polymesh

TopologyPlugin.cc

@@ -734,12 +734,12 @@ void TopologyPlugin::collapse_edge(QMouseEvent* _event) {
            if ( (hit_point - to).sqrnorm() > (hit_point - from).sqrnorm() )
               closest_edge = m.opposite_halfedge_handle(closest_edge);
 
-//           if ( m.is_collapse_ok(closest_edge) ){
+           if ( m.is_collapse_ok(closest_edge) ){
   //             m.point(m.to_vertex_handle(closest_edge)) = hit_point;
               m.collapse(closest_edge );
               m.garbage_collection();
-//           } else
-//             emit log(LOGERR,"Collapse is not allowed here!");
+           } else
+             emit log(LOGERR,"Collapse is not allowed here!");
 
            emit log(LOGOUT,"Picked Edge " + QString::number(closest_edge.idx()));