message: test if !end before accessing operator
diff: @@ -179,7 +179,7 @@ class Witness_complex {
  norelax_dist2 = l_it->second;
  }
  } else if (dim == 0) {
  - for (; l_it->second - alpha2 <= norelax_dist2 && l_it != end; ++l_it) {
  + for (;l_it != end && l_it->second - alpha2 <= norelax_dist2; ++l_it) {
  simplex.push_back(l_it->first);
  double filtration_value = 0;
  // if norelax_dist is infinite, relaxation is 0.
  