MT#58352 lb_and_extra_sockets_sync() fix undef extra_socket

* $extra_sockets_config can be undef, a check for undef
  and that the value is a HASH ref is added to prevent
  unexpected behaviour

Change-Id: I6914a8d4eddc7f35ba69fe92c7acc130c0475aca
(cherry picked from commit 9d7fdb3)

helper/sync-db

@@ -125,7 +125,11 @@ sub lb_and_extra_sockets_sync {
 
     generic_enum_sync(
         $dbh,
-        { %lb_pairs, %{$extra_sockets_config} },
+        { %lb_pairs,
+          $extra_sockets_config && ref $extra_sockets_config eq 'HASH'
+            ? %{$extra_sockets_config}
+            : (),
+        },
         $usr_pref, $dom_pref, $peer_pref,
         $pref_name
     );