message: Update Spec::m_enumkeys when any column is erased rather than just enum columns
diff: @@ -323,8 +323,12 @@ void Spec::erase_column(size_t column_ndx)
  else if (is_string_enum_type(column_ndx)) {
  // Enum columns do also have a separate key list
  ref_type keys_ref = m_enumkeys.get_as_ref(column_ndx);
  -
  Array::destroy_deep(keys_ref, m_top.get_alloc());
  + m_enumkeys.set(column_ndx, 0);
  + }
  +
  + // Remove this column from the enum keys lookup and clean it up if it's now empty
  + if (m_enumkeys.is_attached()) {
  m_enumkeys.erase(column_ndx); // Throws
  bool all_empty = true;
  for (size_t i = 0; i < m_enumkeys.size(); i++) {
  