QQ: Fix crash bug when reaching delivery limit

This only happens when using basic.get but would crash the quorum queue
when the delivery limit was reached due to the transient basic.get
consumer being removed

1 files changed, 13 insertions, 7 deletions

diff --git a/src/rabbit_fifo.erl b/src/rabbit_fifo.erl
index 940ed0d999..3a0fe2442a 100644
--- a/src/rabbit_fifo.erl
+++ b/src/rabbit_fifo.erl
@@ -1141,13 +1141,19 @@ return(#{index := IncomingRaftIdx} = Meta, ConsumerId, Returned,
                                   return_one(MsgId, MsgNum, Msg, S0, E0,
                                              ConsumerId)
                           end, {State0, Effects0}, Returned),
-    #{ConsumerId := Con0} = Cons0 = State1#?MODULE.consumers,
-    Con = Con0#consumer{credit = increase_credit(Con0, map_size(Returned))},
-    {Cons, SQ, Effects2} = update_or_remove_sub(ConsumerId, Con, Cons0,
-                                                SQ0, Effects1),
-    State2 = State1#?MODULE{consumers = Cons,
-                            service_queue = SQ},
-    {State, ok, Effects} = checkout(Meta, State2, Effects2),
+    {State2, Effects3} =
+        case State1#?MODULE.consumers of
+            #{ConsumerId := Con0} = Cons0 ->
+                Con = Con0#consumer{credit = increase_credit(Con0,
+                                                             map_size(Returned))},
+                {Cons, SQ, Effects2} = update_or_remove_sub(ConsumerId, Con,
+                                                            Cons0, SQ0, Effects1),
+                {State1#?MODULE{consumers = Cons,
+                               service_queue = SQ}, Effects2};
+            _ ->
+                {State1, Effects1}
+        end,
+    {State, ok, Effects} = checkout(Meta, State2, Effects3),
     update_smallest_raft_index(IncomingRaftIdx, State, Effects).
 
 % used to processes messages that are finished