When we click "Mail Command Action" of mail commander plugin it is resulting in

INF/lib/classes.jar!/com/gmail/sikakura/MailCommandTrigger/MailCommandAction/index.jelly:3:59: <st:include> No page found 'sidepanel.jelly' for class com.gmail.sikakura.MailCommandTrigger$MailCommandAction
at org.kohsuke.stapler.jelly.JellyClassTearOff.serveIndexJelly(JellyClassTearOff.java:117)
at org.kohsuke.stapler.jelly.JellyFacet.handleIndexRequest(JellyFacet.java:127)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:735)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:876)
at org.kohsuke.stapler.MetaClass$13.dispatch(MetaClass.java:411)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:746)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:876)
at org.kohsuke.stapler.MetaClass$6.doDispatch(MetaClass.java:249)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:746)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:876)