Otherwise, following debugging log will be saved and the checker for
the varlink-idl log triggers failure:
```
systemd-userwork: processing[3110]: varlink-6-6: Parameters for method
io.systemd.UserDatabase.GetUserRecord() didn't pass validation on field 'service': No anode
```
(cherry picked from commit
df25e4af162806e67fac88709413516a8182f634)
(! varlinkctl call "")
(! varlinkctl call "" "")
(! varlinkctl call "" "" "")
-(! varlinkctl call /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetUserRecord </dev/null)
+(! varlinkctl call /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetUserRecord '{ "service" : "io.systemd.ShouldNotExist" }')
(! varlinkctl validate-idl "")
(! varlinkctl validate-idl </dev/null)