message: fix (op-proposer): use safe head in block range
diff: @@ -109,7 +109,12 @@ func (d *Driver) GetBlockRange(
  d.l.Error(name+" unable to get next block number", "err", err)
  return nil, nil, err
  }
  - latestHeader, err := d.cfg.L2Client.HeaderByNumber(ctx, nil)
  + status, err := d.cfg.RollupClient.SyncStatus(ctx)
  + if err != nil {
  + d.l.Error(name+" unable to get sync status", "err", err)
  + return nil, nil, err
  + }
  + latestHeader, err := d.cfg.L2Client.HeaderByNumber(ctx, new(big.Int).SetUint64(status.SafeL2.Number))
  if err != nil {
  d.l.Error(name+" unable to retrieve latest header", "err", err)
  return nil, nil, err
  