Whenever I add the "GitLab commit status publisher" post-build action to my freestyle project and restart Jenkins, on the next startup Jenkins complains "You have data stored in an older format and/or unreadable data".

This fragment is added to the project config.xml:

<publishers>
  <ruby-proxy-object>
    <ruby-object ruby-class="Jenkins::Tasks::PublisherProxy" pluginid="gitlab-hook">
      <object ruby-class="GitlabNotifier" pluginid="gitlab-hook"/>
      <pluginid pluginid="gitlab-hook" ruby-class="String">gitlab-hook</pluginid>
    </ruby-object>
  </ruby-proxy-object>
</publishers>

The "Manage Old Data" screen says:

Type: hudson.model.FreeStyleProject
Name: semic-test
Error: NoSuchMethodError: org.jruby.RubyClass.getVariableAccessorForWrite(Ljava/lang/String;)Lorg/jruby/RubyClass$VariableAccessor;, CannotResolveClassException: pluginid, InstantiationError: null