Fix MSAN error in MoQT Joining FETCH: set the SubscribeWindow correctly when there is no range information in the message.

PiperOrigin-RevId: 735878086

quiche/quic/moqt/moqt_track.h

diff --git a/quiche/quic/moqt/moqt_track.h b/quiche/quic/moqt/moqt_track.h
index b1db0c3..7656e3e 100644
--- a/quiche/quic/moqt/moqt_track.h
+++ b/quiche/quic/moqt/moqt_track.h
@@ -215,11 +215,14 @@
 class UpstreamFetch : public RemoteTrack {
  public:
   UpstreamFetch(const MoqtFetch& fetch, FetchResponseCallback callback)
-      : RemoteTrack(fetch.full_track_name, fetch.fetch_id,
-                    SubscribeWindow(
-                        fetch.start_object,
-                        FullSequence(fetch.end_group,
-                                     fetch.end_object.value_or(UINT64_MAX)))),
+      : RemoteTrack(
+            fetch.full_track_name, fetch.fetch_id,
+            fetch.joining_fetch.has_value()
+                ? SubscribeWindow(0, 0)
+                : SubscribeWindow(
+                      fetch.start_object,
+                      FullSequence(fetch.end_group,
+                                   fetch.end_object.value_or(UINT64_MAX)))),
         ok_callback_(std::move(callback)) {
     // Immediately set the data stream type.
     CheckDataStreamType(MoqtDataStreamType::kStreamHeaderFetch);