Description

When I used the emcute routine, the sub had a double-byte name and I could not accept pub from the PC.

Steps to reproduce the issue

1.Compile main in examples\emcute_mqttsn. Burn write stm32f4.
2.Connect to my server
3.sub a
4.pub a (Pub was successful, but my device did not receive the message)
5.sub asd
6.pub asd(Success to send and receive)

Versions

RIOT-2019.10