Fix CRYPTO frames never being retransmitted

quinn-proto/src/connection.rs

@@ -593,6 +593,7 @@ impl Connection {
                 self.handshake_pending += info.retransmits;
                 self.bytes_in_flight -= info.bytes as u64;
             }
+            debug_assert!(!self.handshake_pending.is_empty());
             self.handshake_count += 1;
         } else if self.loss_time != 0 {
             // Early retransmit or Time Loss Detection
@@ -2543,6 +2544,7 @@ impl ::std::ops::AddAssign for Retransmits {
         self.rst_stream.extend_from_slice(&rhs.rst_stream);
         self.stop_sending.extend_from_slice(&rhs.stop_sending);
         self.max_stream_data.extend(&rhs.max_stream_data);
+        self.crypto.extend(rhs.crypto.into_iter());
     }
 }