Steps to reproduce:

1. Upgrade from zabbix 5.0

Result:

SNMP discovery rules for "SNMPv2-MIB::sysName.0" or "IF-MIB::ifDescr.1" fail with:

'SNMPv2c agent' checks failed: "Invalid SNMP OID: cannot parse parameter."

Expected:

SNMP discovery rules keep working

SNMP discovery rules set by OID work fine.

snmpget for "SNMPv2-MIB::sysName.0" works fine.

normal item for "SNMPv2-MIB::sysName.0" works fine.

frontend test for "SNMPv2-MIB::sysName.0" works fine.

LLD for "IF-MIB::ifDescr" works fine.