fix(persistent_sessions): protect against looking up stale data

apps/emqx/src/emqx_persistent_session.erl

@@ -179,6 +179,10 @@ timestamp_from_conninfo(ConnInfo) ->
     end.
 
 lookup(ClientID) when is_binary(ClientID) ->
+    case is_store_enabled() of
+        false ->
+            none;
+        true ->
             case lookup_session_store(ClientID) of
                 none -> none;
                 {value, #session_store{session = S} = SS} ->
@@ -186,6 +190,7 @@ lookup(ClientID) when is_binary(ClientID) ->
                         expired        -> {expired, S};
                         persistent     -> {persistent, S}
                     end
+            end
     end.
 
 -spec discard_if_present(binary()) -> 'ok'.