集成环信webIM, 注册的时候失败

失败回调为{"type":17,"data":"{\"error\":\"illegal_argument\",\"timestamp\":1492572733207,\"duration\":0,\"exception\":\"java.lang.IllegalArgumentException\",\"error_description\":\"username [null] is not legal\"}"},
h5里面只导入了三个js文件
 
 
,不清楚是哪里错了, 求解