环信_iOS

自动登陆后收的消息导致程序crash

如题。崩溃时函数栈见附件。崩溃时console里输出如下：
RECV: {"from":null,"to":"13752450315","bodies":[{"action":"deleteAction","type":"cmd"}],"ext":{"groupId":"138095541996225092","content":"","groupname":null}}EaseMob-Group{"from":null,"to":"13752450315","bodies":[{"action":"deleteAction","type":"cmd"}],"ext":{"groupId":"138092905217655352","content":"","groupname":null}}{"from":null,"to":"13752450315","bodies":[{"action":"deleteAction","type":"cmd"}],"ext":{"groupId":"138095541996225092","content":"","groupname":null}}delete-group

SEND:

-[NSNull stringByTrimmingCharactersInSet:]: unrecognized selector sent to instance 0x19e832ea8

看起来像是传过来的消息里from或groupname没有导致解析失败导致的。这种情况下该如何处理？