message: fix NVM bug
  This bug prevented the user from saving the configuration more than
  twice without rebooting.
diff: @@ -362,10 +362,12 @@ int NVM_commit(void) {
  read_sector_ = 1 - read_sector_;
  // invalidate the other sector
  - if (read_sector->index < read_sector->n_data)
  + if (read_sector->index < read_sector->n_data) {
  status = set_allocation_state(read_sector, read_sector->index, 1, INVALID);
  - else
  + read_sector->index += 1;
  + } else {
  status = erase(read_sector);
  + }
  return status;
  }
  