Fix filters not clearing on clear button click

Fixes a bug where clearing plain text search would not
refetch unfiltered results.

ee/app/assets/javascripts/requirements/components/requirements_root.vue

@@ -462,16 +462,18 @@ export default {
     },
     handleFilterRequirements(filters = []) {
       const authors = [];
+      let textSearch = '';
 
       filters.forEach(filter => {
         if (typeof filter === 'string') {
-          this.textSearch = filter;
+          textSearch = filter;
         } else if (filter.value.data !== ANY_AUTHOR) {
           authors.push(filter.value.data);
         }
       });
 
       this.authorUsernames = [...authors];
+      this.textSearch = textSearch;
       this.currentPage = 1;
       this.prevPageCursor = '';
       this.nextPageCursor = '';

ee/spec/frontend/requirements/components/requirements_root_spec.js

@@ -667,6 +667,18 @@ describe('RequirementsRoot', () => {
           `http://localhost/?page=1&state=opened&search=foo&sort=created_desc&author_username%5B%5D=root&author_username%5B%5D=john.doe`,
         );
       });
+
+      it('updates props `textSearch` and `authorUsernames` with empty values when passed filters param is empty', () => {
+        wrapper.setData({
+          authorUsernames: ['foo'],
+          textSearch: 'bar',
+        });
+
+        wrapper.vm.handleFilterRequirements([]);
+
+        expect(wrapper.vm.authorUsernames).toEqual([]);
+        expect(wrapper.vm.textSearch).toBe('');
+      });
     });
 
     describe('handleSortRequirements', () => {