Fix loading authors in issues list

Changelog: fixed

app/assets/javascripts/vue_shared/components/filtered_search_bar/tokens/author_token.vue

 <script>
 import { GlAvatar, GlFilteredSearchSuggestion } from '@gitlab/ui';
-
+import { compact } from 'lodash';
 import createFlash from '~/flash';
 import { __ } from '~/locale';
 
@@ -59,8 +59,10 @@ export default {
         .then((res) => {
           // We'd want to avoid doing this check but
           // users.json and /groups/:id/members & /projects/:id/users
-          // return response differently.
-          this.authors = Array.isArray(res) ? res : res.data;
+          // return response differently
+
+          // TODO: rm when completed https://gitlab.com/gitlab-org/gitlab/-/issues/345756
+          this.authors = Array.isArray(res) ? compact(res) : compact(res.data);
         })
         .catch(() =>
           createFlash({

spec/frontend/vue_shared/components/filtered_search_bar/tokens/author_token_spec.js

@@ -112,6 +112,35 @@ describe('AuthorToken', () => {
         });
       });
 
+      // TODO: rm when completed https://gitlab.com/gitlab-org/gitlab/-/issues/345756
+      describe('when there are null users presents', () => {
+        const mockAuthorsWithNullUser = mockAuthors.concat([null]);
+
+        beforeEach(() => {
+          jest
+            .spyOn(wrapper.vm.config, 'fetchAuthors')
+            .mockResolvedValue({ data: mockAuthorsWithNullUser });
+
+          getBaseToken().vm.$emit('fetch-suggestions', 'root');
+        });
+
+        describe('when res.data is present', () => {
+          it('filters the successful response when null values are present', () => {
+            return waitForPromises().then(() => {
+              expect(getBaseToken().props('suggestions')).toEqual(mockAuthors);
+            });
+          });
+        });
+
+        describe('when response is an array', () => {
+          it('filters the successful response when null values are present', () => {
+            return waitForPromises().then(() => {
+              expect(getBaseToken().props('suggestions')).toEqual(mockAuthors);
+            });
+          });
+        });
+      });
+
       it('calls `createFlash` with flash error message when request fails', () => {
         jest.spyOn(wrapper.vm.config, 'fetchAuthors').mockRejectedValue({});