Also listen on other enter button and empty entry after sending.
Co-Authored-By: ialokim <ialokim@t-online.de>
Inspired by https://code.briarproject.org/grote/briar-cli-python-demo/blob/8ced7b9f37e6ee59dac6042c9bcf21c54c648e9e/briar-cli.py.
GTK isn't thread safe. Therefore, I was experiencing race conditions.
Reading Briar's output isn't much reliable.
