Zabbix agent reports unsupported item if WMI reports empty search result.

Zabbix agent item wmi.getall gets unsupported if the wmi query reports empty data.

Create item key:

wmi.getall[root\cimv2,"SELECT IDProcess,Name FROM Win32_PerfFormattedData_PerfProc_Process WHERE Name = 'non_existing_process'"] 

Expected result = just empty data, because query is valid.

Empty data-set is also a valid response, this only means that the query returned empty result. By example, this can be used in process monitoring using wmi, where some process may be stopped for a while. In this scenario, items gets unsupported, and process monitoring will be stopped until next unsupported item check interval. 

If the item will just report empty data, preprocessing steps can be used to put correct values like 0 processes running in dependent items, and triggers can be configured.

I expect this item to work in following way:

• data if query returns some data
• empty data if query returns no data
• unsupported, if there is a syntax error in the query