gen_packets crashes when stdin input does not contain ':'

[alexandrasandulescu]

I tested this issue on Ubuntu 16.04 package, Ubuntu 20.4 package and on master branch. It reproduces on all of them.

Steps to reproduce:

echo -n "test" | gen_packets -o x.wav -

I discovered this issue when working on defcon2020 mooodem challenge.

[wb2osz]

Now available in dev branch which will eventually become version 1.6,
Thanks for pointing this out.

Good luck in the challenge.

part of commit 0661e23 since I was already in the middle of updating that file.