我有一個接口員工：export interface Employee {  firstName: string;  lastName: string;}我正在嘗試將 Employee 類型的元素推入數組，如下所示：  let allEmployees: Employee[] = [];  allEmployees = emp.data?.map((employee) => {    return { firstName: employee.firstName, lastName: employee.lastName }  });我收到以下打字稿編譯時錯誤：type 'undefined' is not assignable to type 'Employee[]'我使用 .map 函數返回數組的最終值。我該如何解決這個問題？