DQT: be extra defensive in a couple more places

References #11541, #12109, #12821, #13837.

(cherry picked from commit a8901bc)

Author: michaelklishin

deps/rabbit/src/rabbit_amqqueue.erl

@@ -765,6 +765,7 @@ augment_declare_args(VHost, Durable, Exclusive, AutoDelete, Args0) ->
     case vhost:get_metadata(V) of
         #{default_queue_type := DefaultQueueType}
           when is_binary(DefaultQueueType) andalso
+               DefaultQueueType =/= <<"undefined">> andalso
                not HasQTypeArg ->
             update_args_table_with_queue_type(DefaultQueueType, Durable, Exclusive, AutoDelete, Args0);
         _ ->

deps/rabbit/src/rabbit_vhost.erl

@@ -713,6 +713,8 @@ i(metadata, VHost) ->
             #{default_queue_type => DQT};
         M = #{default_queue_type := undefined} ->
             M#{default_queue_type => DQT};
+        M = #{default_queue_type := <<"undefined">>} ->
+            M#{default_queue_type => DQT};
         M = #{default_queue_type := QT} ->
             M#{default_queue_type => rabbit_queue_type:short_alias_of(QT)};
         M when is_map(M) ->