Steps to reproduce:

1. Use FreeBSD 8.2 or earlier
2. Use agent 4.0.31, 5.0.12, 5.2.7, 5.4.1, 6.0.0 or older
3. Specify any cmdline value for proc.num[] or proc.mem[]

# ps ax -o user,command | grep syslogd
root /usr/sbin/syslogd -ss
# zabbix_get -s 127.0.0.1 -k 'proc.num[syslogd,root]'
1

Result:
Returned 0.

FreeBSD 7.4, 8.2; zabbix_agentd 5.4.1:

# zabbix_get -s 127.0.0.1 -k 'proc.num[syslogd,root,,s$]'
0

Expected:
Not 0.

FreeBSD 8.3, 9.0; zabbix_agentd 5.4.1:

# zabbix_get -s 127.0.0.1 -k 'proc.num[syslogd,root,,s$]'
1

As far as I can tell, the solution to ZBX-19139 affected the get_commandline() function in proc.c on older versions of FreeBSD.

FreeBSD 7.4, 8.2; zabbix_agentd 5.4.0:

# zabbix_get -s 127.0.0.1 -k 'proc.num[syslogd,root,,s$]'
1