As of version 2.17.0 the verified "vote" is not sent at all to Gerrit (removed from the command line/rest call) unless there is an actual value to be sent. So if you change the configuration to contain only values for code review and empty strings for verified you won't get the error.
Version 2.29.0 (released Feb 15 2019)
- Java 8 and Jenkins 1.121 (#389, #390)
- Support triggering for wip-state-changed and private-state-changed (#383)
- Start the trigger in a known state when using a dynamic configuration URL (#350)
- JENKINS-55262 - Missing content-type on serverStatuses REST API (#388)
Version 2.28.0 (released Dec 19 2018)