Steps to reproduce:

1. Setup old zabbix
2. Configure bunch of LLD rules for many hosts
3. Update to zabbix-3.4
4. Update to zabbix-4.2
5. Look at zabbix_server.log

Result:
Regular error messages in zabbix_server.log:

zabbix_server [2093]: ERROR file:lld_item.c,line:3763 Something impossible has just happened.
  2093:20190710:142759.482 === Backtrace: ===
  2093:20190710:142759.482 12: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](zbx_backtrace+0x42) [0x55706ebf6e6a]
  2093:20190710:142759.482 11: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](+0x114663) [0x55706eb70663]
  2093:20190710:142759.482 10: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](+0x1147f8) [0x55706eb707f8]
  2093:20190710:142759.482 9: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](lld_update_items+0x3a8) [0x55706eb74251]
  2093:20190710:142759.482 8: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](lld_process_discovery_rule+0x3e7) [0x55706eb58c97]
  2093:20190710:142759.482 7: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](+0xfaaae) [0x55706eb56aae]
  2093:20190710:142759.482 6: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](lld_worker_thread+0x357) [0x55706eb571bb]
  2093:20190710:142759.482 5: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](zbx_thread_start+0x37) [0x55706ec047d8]
  2093:20190710:142759.482 4: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](MAIN_ZABBIX_ENTRY+0xf6e) [0x55706ea9c8a2]
  2093:20190710:142759.482 3: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](daemon_start+0x2f6) [0x55706ebf66ae]
  2093:20190710:142759.482 2: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](main+0x312) [0x55706ea9b932]
  2093:20190710:142759.482 1: /lib64/libc.so.6(__libc_start_main+0xf5) [0x7f7a845cc495]
  2093:20190710:142759.482 0: /usr/sbin/zabbix_server: lld worker #1 [processed 1 LLD rules, idle 60.064235 sec during 60.103774 sec](+0x3e9f9) [0x55706ea9a9f9]

Expected:
Silence in log.