message: prevent bad access on new chains
diff: @@ -254,8 +254,8 @@ struct controller_impl {
  initialize_fork_db(); // set head to genesis state
  auto end = blog.read_head();
  - auto end_time = end->timestamp.to_time_point();
  if( end && end->block_num() > 1 ) {
  + auto end_time = end->timestamp.to_time_point();
  replaying = true;
  replay_head_time = end_time;
  ilog( "existing block log, attempting to replay ${n} blocks", ("n",end->block_num()) );
  