Steps to reproduce:

1. Create item with type SNMP agent
2. Fill in name and key fields (field "SNMP OID" is empty)
3. Press "Test" item
4. Press "Get value and test"

Result:
misleading message "Value was not provided for the preprocessing test."
Expected:
for example in 6.0 "snmp_parse_oid(): cannot parse OID ""." but it is also not so user-friendly