Fix javascript error for when there are no issues

app/assets/javascripts/filtered_search/filtered_search_manager.js.es6

@@ -3,9 +3,11 @@
 (() => {
   class FilteredSearchManager {
     constructor() {
-      this.tokenizer = gl.FilteredSearchTokenizer;
       this.filteredSearchInput = document.querySelector('.filtered-search');
       this.clearSearchButton = document.querySelector('.clear-search');
+
+      if (this.filteredSearchInput) {
+        this.tokenizer = gl.FilteredSearchTokenizer;
         this.dropdownManager = new gl.FilteredSearchDropdownManager();
 
         this.bindEvents();
@@ -15,6 +17,7 @@
         this.cleanupWrapper = this.cleanup.bind(this);
         document.addEventListener('page:fetch', this.cleanupWrapper);
       }
+    }
 
     cleanup() {
       this.unbindEvents();