We are experiencing an issue where Zabbix enters an infinite loop during BulkRequest processing when a user carries out the following steps:

1. Using an SNMP template to a host
2. Checks item and LLD rule values with the 'Test' function
3. Changes the monitoring interval to 1 hour
4. Starts monitoring
5. Manually retrieves monitoring data using 'Execute Now'

We've tried to reproduce the issue following the same steps as the user, we have been unsuccessful. However, this issue has already occurred twice in the user's environment, suggesting that there is some degree of reproducibility.

Due to this issue, the task manager enters an infinite loop, and we have not found any recovery method other than a restart.

We suspect the issue arises when a request is made with max_vars=0. The current source code does not handle this scenario, causing the task manager to become trapped in an infinite loop.

2385953:20230518:201928.571 log level has been increased to 4 (debug)
2385953:20230518:201928.573 zbx_snmp_walk() snmp_synch_response() status:0 s_snmp_errno:0 errstat:0 max_vars:0
2385953:20230518:201928.576 zbx_snmp_walk() snmp_synch_response() status:0 s_snmp_errno:0 errstat:0 max_vars:0
2385953:20230518:201928.578 zbx_snmp_walk() snmp_synch_response() status:0 s_snmp_errno:0 errstat:0 max_vars:0
2385953:20230518:201928.580 zbx_snmp_walk() snmp_synch_response() status:0 s_snmp_errno:0 errstat:0 max_vars:0
2385953:20230518:201928.582 zbx_snmp_walk() snmp_synch_response() status:0 s_snmp_errno:0 errstat:0 max_vars:0
2385953:20230518:201928.584 zbx_snmp_walk() snmp_synch_response() status:0 s_snmp_errno:0 errstat:0 max_vars:0
...