feat(client): resolve type errors in token storage service

apps/client/src/app/pages/admin/admin-page.component.ts

@@ -103,7 +103,7 @@ export class AdminPageComponent {
     const token = this.tokenStorageService.getToken();
 
     document.cookie = [
-      `${BULL_BOARD_COOKIE_NAME}=${encodeURIComponent(token)}`,
+      `${BULL_BOARD_COOKIE_NAME}=${encodeURIComponent(token ?? '')}`,
       'path=/',
       'SameSite=Strict'
     ].join('; ');

apps/client/src/app/pages/demo/demo-page.component.ts

@@ -25,7 +25,7 @@ export class GfDemoPageComponent {
   }
 
   public ngOnInit() {
-    const hasToken = this.tokenStorageService.getToken()?.length > 0;
+    const hasToken = !!this.tokenStorageService.getToken();
 
     if (hasToken) {
       this.notificationService.alert({

apps/client/src/app/services/token-storage.service.ts

@@ -6,9 +6,9 @@ import { KEY_TOKEN } from './settings-storage.service';
   providedIn: 'root'
 })
 export class TokenStorageService {
-  public getToken(): string {
+  public getToken(): string | null {
     return (
-      window.sessionStorage.getItem(KEY_TOKEN) ||
+      window.sessionStorage.getItem(KEY_TOKEN) ??
       window.localStorage.getItem(KEY_TOKEN)
     );
   }