Check_MK Werk 6381: apc_inrow_system_events, liebert_system_events: Fixed handling of empty section

ID: 6381 Title: apc_inrow_system_events, liebert_system_events: Fixed handling of empty section Component: Checks & agents Level: 1 Class: Bug fix Version: 1.6.0i1 If no events are reported for these two checks, the agent section is empty and Check_MK marked the related services as 'vanished'. An empty section is valid and these two checks can handle them correctly.