Add explicit != nullptr check in quic_session. No behavior change.

net/quic/core/quic_session.cc

Index: net/quic/core/quic_session.cc
diff --git a/net/quic/core/quic_session.cc b/net/quic/core/quic_session.cc
index 6c3add0cfefdb7fceabd0a8db168b7cba149e077..2cba5f1d17dd04016d8d7bc0e2383eeb8becc1d2 100644
--- a/net/quic/core/quic_session.cc
+++ b/net/quic/core/quic_session.cc
@@ -159,7 +159,7 @@ void QuicSession::OnWindowUpdateFrame(const QuicWindowUpdateFrame& frame) {
     return;
   }
   ReliableQuicStream* stream = GetOrCreateStream(stream_id);
-  if (stream) {
+  if (stream != nullptr) {
     stream->OnWindowUpdateFrame(frame);
   }
 }