message: Avoid crashing while calculating now - loss_delay
diff: @@ -401,14 +401,11 @@ impl LossRecoverySpace {
  // Housekeeping.
  self.remove_old_lost(now, cleanup_delay);
  - // Packets sent before this time are deemed lost.
  - let lost_deadline = now - loss_delay;
  qtrace!(
  - "detect lost {}: now={:?} delay={:?} deadline={:?}",
  + "detect lost {}: now={:?} delay={:?}",
  self.space,
  now,
  loss_delay,
  - lost_deadline
  );
  self.first_ooo_time = None;
  @@ -423,12 +420,13 @@ impl LossRecoverySpace {
  // BTreeMap iterates in order of ascending PN
  .take_while(|(&k, _)| Some(k) < largest_acked)
  {
  - if packet.time_sent <= lost_deadline {
  + // Packets sent before now - loss_delay are deemed lost.
  + if packet.time_sent + loss_delay <= now {
  qtrace!(
  - "lost={}, time sent {:?} is before lost_deadline {:?}",
  + "lost={}, time sent {:?} is before lost_delay {:?}",
  pn,
  packet.time_sent,
  - lost_deadline
  + loss_delay
  );
  } else if largest_acked >= Some(*pn + PACKET_THRESHOLD) {
  qtrace!(
  