fix(shared): ensure sticky strategy sticks to the first pick

Prior to this fix, the alive pids are never inserted due to a
missing insert when handing remote pids from mnesia event.

CHANGES-4.3.md

@@ -64,6 +64,13 @@ File format:
   This issue only occurs when unsubscribe with the session kept.
   Fixed in [#9119](https://github.com/emqx/emqx/pull/9119)
 
+- Fix shared subscription 'sticky' strategy when there is no local subscriptions at all.
+  Prior to this change, it may take a few rounds to randomly pick group members until a local subscriber
+  is hit (and then start sticking to it).
+  After this fix, it will start sticking to whichever randomly picked member even when it is a
+  subscriber from another node in the cluster.
+  Fixed in [#9122](https://github.com/emqx/emqx/pull/9122)
+
 ## v4.3.20
 
 ### Bug fixes

src/emqx_shared_sub.erl

@@ -456,6 +456,7 @@ handle_cast(Msg, State) ->
 
 handle_info({mnesia_table_event, {write, NewRecord, _}}, State = #state{pmon = PMon}) ->
     #emqx_shared_subscription{subpid = SubPid} = NewRecord,
+    ok = maybe_insert_alive_tab(SubPid),
     {noreply, update_stats(State#state{pmon = emqx_pmon:monitor(SubPid, PMon)})};
 
 %% The subscriber may have subscribed multiple topics, so we need to keep monitoring the PID until