我做的项目是会有不断的生成预制(有RigidBody和BoxCollider)，在运动到终点时再回收到Pool中，有概率报如下错误laya.physics.js:430 Uncaught TypeError: Cannot read property 'GetType' of null

    at box2d.b2Fixture.GetType (laya.physics.js:430)
    at box2d.b2ContactFactory.Create (laya.physics.js:576)
    at box2d.b2ContactManager.AddPair (laya.physics.js:586)
    at box2d.b2BroadPhase.UpdatePairs (laya.physics.js:308)
    at box2d.b2ContactManager.FindNewContacts (laya.physics.js:584)
    at box2d.b2World.Solve (laya.physics.js:799)
    at box2d.b2World.Step (laya.physics.js:811)
    at Physics._update (laya.physics.js:2003)
    at TimerHandler.run (laya.core.js:21423)
    at Timer._update (laya.core.js:21262)

相关逻辑代码如下：
[code] moveSuccess(){

        this.owner.removeSelf();
        Laya.Pool.recover("flyCat", this.owner)
    }
    onTriggerEnter(other: any, self: any, contact: any): void {
        if (other.label === "cloud") {
            Laya.Tween.clearAll(this._sp)
            let effect: Laya.Animation = Laya.Pool.getItemByCreateFun("deathEffect", this.createEffect, this);
            effect.pos(this._sp.x, this._sp.y);
            this._sp.parent.addChild(effect);
            effect.play(0, false);
            this.owner.removeSelf();
            Laya.Pool.recover("flyCat", this.owner)
        }
    }

    createEffect(): Laya.Animation {
        let ani: Laya.Animation = new Laya.Animation();
        ani.loadAnimation("catFly.ani");
        ani.on(Laya.Event.COMPLETE, null, recover);
        function recover(): void {
            ani.removeSelf();
            Laya.Pool.recover("deathEffect", ani);
        }
        return ani;
    }[/code]