AVUser子类化中包括AVRelation之后不能转换成指定的类型

Question

子类如下

public class Account extends AVUser {

    public Account() {   }

    public void setNickName(String name){
        put("nickName", name);
    }

    public String getNickName(){
        return getString("nickName");
    }

    public String getAvatar(){
        AVFile file = getAVFile("avatar");
        if (file == null){
            return "assets://ic_avatar.png";
        } else {
            return file.getUrl();
        }
    }
    public void setAvatar(String filePath){
        try {
            AVFile file  = AVFile.withAbsoluteLocalPath(new File(filePath).getName(), filePath);
            put("avatar", file );
        } catch (IOException ignored) {

        }
    }

    public AVRelation<Tweet> getLikes() {
        AVRelation<Tweet> relation = getRelation("likes");
        return relation;
    }

    public void removeLikes(Tweet tweet) {
        AVRelation<Tweet> likes = getLikes();
        likes.remove(tweet);
        this.saveInBackground();
    }
    public void addLiker(Tweet tweet) {
        AVRelation<Tweet> likes = getLikes();
        likes.add(tweet);
        this.saveInBackground();
    }

服务端的likes字段如下

现在每次调用AVUser.getCurrentUser(Account.class)都会报错，以前没添加likes之前没有问题

可能相关的错误信息
t java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.alibaba.fastjson.util.FieldInfo.get(FieldInfo.java:220) at com.alibaba.fastjson.serializer.FieldSerializer.getPropertyValue(FieldSerializer.java:88) at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:148) at com.alibaba.fastjson.serializer.CollectionSerializer.write(CollectionSerializer.java:96) at com.alibaba.fastjson.serializer.ObjectFieldSerializer.writeProperty(ObjectFieldSerializer.java:116) at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:180) at com.alibaba.fastjson.serializer.MapSerializer.write(MapSerializer.java:130) at com.alibaba.fastjson.serializer.ObjectFieldSerializer.writeProperty(ObjectFieldSerializer.java:111) at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:180) at com.alibaba.fastjson.serializer.JSONSerializer.write(JSONSerializer.java:330) at com.alibaba.fastjson.JSON.toJSONString(JSON.java:388) at com.avos.avoscloud.AVUser.cast(AVUser.java:1633) at com.avos.avoscloud.AVUser.getCurrentUser(AVUser.java:154)