Remove recent searches when not available

The default value of `[]` does not make the recent searches
section hidden, thus `null` needs to be used.

app/assets/javascripts/vue_shared/components/filtered_search_bar/filtered_search_bar_root.vue

@@ -83,7 +83,7 @@ export default {
     return {
       initialRender: true,
       recentSearchesPromise: null,
-      recentSearches: [],
+      recentSearches: null,
       filterValue: this.initialFilterValue,
       selectedSortOption,
       selectedSortDirection,

ee/changelogs/unreleased/229584-jira-issues-ui-polish.yml

+---
+title: Polish Jira issues UI
+merge_request: 37095
+author:
+type: changed