Latest ocserv crashes (0.12.0 and @ bbc79584) on Ubuntu 16.04

Commit https://gitlab.com/ocserv/ocserv/commit/cf8304cadf7008a086860e0abcbba03b969fcb20 broke something, earlier versions are working ok.

# lsb_release -d
Description:    Ubuntu 16.04.4 LTS

# ./ocserv -v
ocserv 0.12.0

Compiled with: seccomp, tcp-wrappers, oath, gssapi, PAM, PKCS#11, AnyConnect
GnuTLS version: 3.4.10

# ./ocserv --foreground  -d 9999
note: setting 'pam' as primary authentication method
note: setting 'file' as supplemental config option
listening (TCP) on 0.0.0.0:443...
listening (TCP) on [::]:443...
listening (UDP) on 0.0.0.0:443...
listening (UDP) on [::]:443...
ocserv[10115]: main: initializing control unix socket: /var/run/occtl.socket
ocserv[10115]: main: initialized ocserv 0.12.0
*** Error in `ocserv-s': free(): invalid pointer: 0x0000000001554040 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x777e5)[0x7ff98bcbf7e5]
/lib/x86_64-linux-gnu/libc.so.6(+0x8037a)[0x7ff98bcc837a]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7ff98bccc53c]
/usr/lib/x86_64-linux-gnu/libgnutls.so.30(gnutls_certificate_free_keys+0x67)[0x7ff98dddf797]
/usr/lib/x86_64-linux-gnu/libgnutls.so.30(gnutls_certificate_free_credentials+0x1f)[0x7ff98dddf92f]
ocserv-s[0x419e6f]
ocserv-s[0x43f984]
ocserv-s[0x43fc23]
ocserv-s[0x40b527]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7ff98bc68830]
ocserv-s[0x4076d9]
======= Memory map: ========
<... skip ...>
ocserv[10115]: main: main.c:943: Sec-mod 10116 died with signal 6
ocserv[10115]: main: main.c:947: ocserv-secmod died unexpectedly
ocserv[10115]: main: termination request received; waiting for children to die
ocserv[10115]: main: main-sec-mod-cmd.c:106: command socket for sec-mod closed
ocserv[10115]: main: main.c:1203: error in command from sec-mod
ocserv[10115]: main: termination request received; waiting for children to die
*** Error in `ocserv-m': free(): invalid pointer: 0x0000000001554040 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x777e5)[0x7ff98bcbf7e5]
/lib/x86_64-linux-gnu/libc.so.6(+0x8037a)[0x7ff98bcc837a]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7ff98bccc53c]
/usr/lib/x86_64-linux-gnu/libgnutls.so.30(gnutls_certificate_free_keys+0x67)[0x7ff98dddf797]
/usr/lib/x86_64-linux-gnu/libgnutls.so.30(gnutls_certificate_free_credentials+0x1f)[0x7ff98dddf92f]
ocserv-m[0x419e6f]
ocserv-m[0x428f98]
ocserv-m[0x40bc74]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7ff98bc68830]
ocserv-m[0x4076d9]
======= Memory map: ========
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