Cannot read properties of null (reading 'getComponent')circle碰撞检测报错

下面是报错的代码,主要是想监听碰撞的物体,但是我在另一个ts文件写代码时用boxCollider2D却不会报错,用circleCollider2D却会。
start() {

    // 获取碰撞事件得物理形状

    this.circleCollider2D = this.football.getComponent(CircleCollider2D);

    this.circleCollider2D.on(Contact2DType.BEGIN_CONTACT, this.OnBeginContact, this);

}

onDestroy() {

    this.circleCollider2D.off(Contact2DType.BEGIN_CONTACT, this.OnBeginContact, this);

}

// 碰撞检测

OnBeginContact(self, other): void {

    if (other.node._name == "player") {

        console.log("碰到足球啦");

    }

}![1677646780529|600x170](upload://dEZkW4lzUlamQV4vZvOCnNWwWrL.png)

1677646780529

这是报错信息,还请同志开道一二