message: Gracefully handle want_read returned by read_some
diff: @@ -150,6 +150,8 @@ bool stream::handle_read_result(rw_state read_result, size_t rb) {
  backend().add(operation::write, fd(), this);
  wr_op_backoff_ = false;
  }
  + [[fallthrough]];
  + case rw_state::want_read:
  if (rb == 0)
  return false;
  collected_ += rb;
  @@ -162,9 +164,6 @@ bool stream::handle_read_result(rw_state read_result, size_t rb) {
  }
  }
  break;
  - case rw_state::want_read:
  - CAF_LOG_ERROR("handle_read_result encountered rw_state::want_read");
  - return false;
  }
  return true;
  }
  