如何使mat-select第一个选项为空？

<mat-form-field>
  <mat-select placeholder="选择项" [formControl]="myControl">
    <mat-option></mat-option>
    <mat-option *ngFor="let option of options" [value]="option.value">{{ option.label }}</mat-option>
  </mat-select>
</mat-form-field>

import { Component } from '@angular/core';
import { FormControl } from '@angular/forms';

@Component({
  selector: 'app-my-component',
  templateUrl: './my-component.component.html',
  styleUrls: ['./my-component.component.css']
})
export class MyComponent {
  myControl = new FormControl();
  options = [
    { value: 'option1', label: '选项1' },
    { value: 'option2', label: '选项2' },
    { value: 'option3', label: '选项3' }
  ];
}

constructor() {
  this.myControl.setValue(null);
}