Proxy 6.0.0alpha4 crashes when client connects

Steps to reproduce:

I compiled the proxy as a static binary, but letting a client connect results in the proxy crashing.

zabbix_proxy: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, for GNU/Linux 3.2.0, BuildID[sha1]=fc7732c8abc24669fbc2276e343b84ac279b0c75, with debug_info, not stripped

Since the objdump was unworkably huge, I make a copy available here: https://ivo.palli.nl/zabbix_proxy

Result:

I included the config file, crash dump and build instructions. If you need anything else, please let me know.

Expected:

For the proxy not to crash.