add troubleshoot hint for case when change-list is empty
add troubleshoot hint for case when change-list is empty

uwolfer/gerrit-intellij-plugin,sstafford/gerrit-rest-java-client,eekboom/gerrit-intellij-plugin,uwolfer/gerrit-rest-java-client,vogellacompany/gerrit-rest-java-client,sstafford/gerrit-rest-java-client,vogellacompany/gerrit-rest-java-client,uwolfer/gerrit-rest-java-client