message: refactor: downgrade syntax for compat with Apple Clang and macOS 10.12
diff: @@ -36,8 +36,8 @@ namespace Nextclade {
  const auto nucleotideMutations = node.nucleotideMutations();
  for (const auto& mut : nucleotideMutations) {
  const auto& previousNuc = mapFind(tmpMuts, mut.pos);
  - if (previousNuc.has_value() && (previousNuc.value() != mut.refNuc)) {
  - throw ErrorAttachMutationsInconsistentMutation(mut, previousNuc.value());
  + if (previousNuc.has_value() && (*previousNuc != mut.refNuc)) {
  + throw ErrorAttachMutationsInconsistentMutation(mut, *previousNuc);
  }
  // If mutation reverts nucleotide back to what reference had, remove it from the map
  