msgsz = 0的消息调用，一般是什么情况导致的？遇到2种错误

[libla]

第一种是

[:00000008] lua call [a to :8 : 2538482 msgsz = 0] error : lib/skynet.lua:872: lib/skynet.lua:331: lib/skynet.lua:281: attempt to call a boolean value (upvalue 'f')

第二种是

[:00000008] lua call [0 to :8 : 2644537 msgsz = 0] error : lib/skynet.lua:872: lib/skynet.lua:331: cannot resume dead coroutine