searchkick (which defines #reindex) is only mixed into Message at class-load time
when advanced_search_allowed? (enterprise + OPENSEARCH_URL) is true at boot. A spec
that stubs advanced_search_allowed? true without a loaded index makes should_index?
true and fires the reindex callback, raising NoMethodError. Guard on respond_to?
so it no-ops when no index is available (real deployments without search index
already have should_index? false, so behavior is unchanged).