Check that MoqtOutgoingQueue is not empty when pulling from cache.

PiperOrigin-RevId: 983461873

quiche/quic/moqt/moqt_outgoing_queue.cc

diff --git a/quiche/quic/moqt/moqt_outgoing_queue.cc b/quiche/quic/moqt/moqt_outgoing_queue.cc
index ffa22fe..2cbb522 100644
--- a/quiche/quic/moqt/moqt_outgoing_queue.cc
+++ b/quiche/quic/moqt/moqt_outgoing_queue.cc
@@ -100,7 +100,7 @@
     uint64_t group, std::optional<uint64_t> subgroup, uint64_t object,
     uint64_t offset) const {
   QUICHE_DCHECK(subgroup.has_value() && subgroup == 0u);
-  if (group < first_group_in_queue()) {
+  if (queue_.empty() || group < first_group_in_queue()) {
     return std::nullopt;
   }
   if (group > current_group_id_) {