[LayaAir 2.0]这个GetType=null的问题有大神解答下吗

碰到个这样的问题，交流区里有大神说让碰撞方法一帧执行一次，按照大神的方式试了下，但是还是报这个错，有别的解决方法吗？
TypeError: Cannot read property 'GetType' of null
preload.js:55
at box2d.b2Fixture.GetType (file:///D:/Documents/myLaya/test/bin/libs/laya.physics.js:430:204)
 
at box2d.b2ContactFactory.Create (file:///D:/Documents/myLaya/test/bin/libs/laya.physics.js:576:81)
 
at box2d.b2ContactManager.AddPair (file:///D:/Documents/myLaya/test/bin/libs/laya.physics.js:586:140)
 
at box2d.b2BroadPhase.UpdatePairs (file:///D:/Documents/myLaya/test/bin/libs/laya.physics.js:308:193)
 
at box2d.b2ContactManager.FindNewContacts (file:///D:/Documents/myLaya/test/bin/libs/laya.physics.js:584:354)
 
at box2d.b2World.Step (file:///D:/Documents/myLaya/test/bin/libs/laya.physics.js:810:170)
 
at Physics.__proto._update (file:///D:/Documents/myLaya/test/bin/libs/laya.physics.js:1792:14)
 
at TimerHandler.__proto.run (file:///D:/Documents/myLaya/test/bin/libs/laya.core.js:7533:45)
 
at Timer.__proto._update (file:///D:/Documents/myLaya/test/bin/libs/laya.core.js:7271:16)
 
at Stage.__proto._updateTimers (file:///D:/Documents/myLaya/test/bin/libs/laya.core.js:31105:21)