Fix warning in EncryptionLevelToProto

quiche/quic/core/quic_trace_visitor.cc: In function 'quic_trace::EncryptionLevel quic::EncryptionLevelToProto(EncryptionLevel)':
quiche/quic/core/quic_trace_visitor.cc:28:1: warning: control reaches end of non-void function [-Wreturn-type]

PiperOrigin-RevId: 531259136

quiche/quic/core/quic_trace_visitor.cc

diff --git a/quiche/quic/core/quic_trace_visitor.cc b/quiche/quic/core/quic_trace_visitor.cc
index 04bbda6..388eebb 100644
--- a/quiche/quic/core/quic_trace_visitor.cc
+++ b/quiche/quic/core/quic_trace_visitor.cc
@@ -22,9 +22,13 @@
     case ENCRYPTION_FORWARD_SECURE:
       return quic_trace::ENCRYPTION_1RTT;
     case NUM_ENCRYPTION_LEVELS:
-      QUIC_BUG(quic_bug_10284_1) << "Invalid encryption level specified";
+      QUIC_BUG(EncryptionLevelToProto.Invalid)
+          << "Invalid encryption level specified";
       return quic_trace::ENCRYPTION_UNKNOWN;
   }
+  QUIC_BUG(EncryptionLevelToProto.Unknown)
+      << "Unknown encryption level specified " << static_cast<int>(level);
+  return quic_trace::ENCRYPTION_UNKNOWN;
 }
 
 QuicTraceVisitor::QuicTraceVisitor(const QuicConnection* connection)