Just wanted to test the plugin and after hitting the next button this exception popped up. Don't know how to proceed. Thank you for your help! 

Stack-Trace

java.lang.NullPointerException at java.util.StringTokenizer.<init>(StringTokenizer.java:199) at java.util.StringTokenizer.<init>(StringTokenizer.java:221) at jenkins.model.Jenkins.getItemByFullName(Jenkins.java:2820) at jenkins.model.Jenkins.getItemByFullName(Jenkins.java:2845) at com.infostretch.labs.actions.ConvertRootAction.doConvert(ConvertRootAction.java:67) at java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:627) at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:343) at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:184) at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:117) at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:130) at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58) at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:739) Caused: javax.servlet.ServletException at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:789) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:870) at org.kohsuke.stapler.MetaClass$10.dispatch(MetaClass.java:384) at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:739) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:870) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:668) at org.kohsuke.stapler.Stapler.service(Stapler.java:238) at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:154) at org.jenkinsci.plugins.ssegateway.Endpoint$SSEListenChannelFilter.doFilter(Endpoint.java:243) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151) at io.jenkins.blueocean.auth.jwt.impl.JwtAuthenticationFilter.doFilter(JwtAuthenticationFilter.java:61) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151) at io.jenkins.blueocean.ResourceCacheControl.doFilter(ResourceCacheControl.java:134) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151) at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:239) at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:215) at net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:88) at org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:114) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151) at jenkins.telemetry.impl.UserLanguages$AcceptLanguageFilter.doFilter(UserLanguages.java:124) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:151) at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:157) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:99) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84) at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87) at jenkins.security.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:117) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87) at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87) at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87) at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87) at jenkins.security.BasicHeaderProcessor.doFilter(BasicHeaderProcessor.java:93) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87) at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249) at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:67) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87) at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:90) at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:171) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:82) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:607) at org.apache.catalina.valves.rewrite.RewriteValve.invoke(RewriteValve.java:277) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:668) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:770) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:748)