test: ajustar aserción para verificar null en allowed_groups

Co-authored-by: aider (openrouter/openai/gpt-5) <aider@aider.chat>

tests/unit/services/admin.test.ts

@@ -114,7 +114,7 @@ describe('AdminService - comandos básicos', () => {
     expect(g == null).toBe(true);
 
     const ag = memdb.query(`SELECT 1 FROM allowed_groups WHERE group_id='g2@g.us'`).get() as any;
-    expect(ag).toBeUndefined();
+    expect(ag == null).toBe(true);
 
     const acount = memdb.query(`SELECT COUNT(*) AS c FROM task_assignments`).get() as any;
     expect(Number(acount.c)).toBe(0);