mqtt:unsubscribe dumps

[dvv]

c = mqtt.Client("foo", 120)
c:connect("192.168.1.4", 1883, 0)
-- NB: http://nodemcu.readthedocs.io/en/dev/en/modules/mqtt/#syntax_7
c:unsubscribe("foo")
-- PANIC: unprotected error in call to Lua API (attempt to call a nil value)

[FrankX0]

You are unsubscribing from a topic you did not subscribe to first. And you seem to mix the client name (foo) and a topic (foo).

[dvv]

I described the sequence on pretty valid calls which led to sudden reset.

[devsaurus]

Thanks for reporting @dvv. It appears that the unsubscribe callback is triggered without being initialized earlier. mud->cb_unsuback_ref is only set when c:unsubscribe() provides a callback function - otherwise it remains uninitialized. I'll dig into a fix.

[pjsg]

Fix merged to dev