java.lang.NullPointerExceptionCaused: java.lang.Error on post build task change

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Stack trace
java.lang.NullPointerException
Caused: java.lang.Error: Failed to instantiate class org.jenkinsci.plugins.postbuildscript.PostBuildScript from {"buildSteps":{"results":[],"role":"BOTH"},"markBuildUnstable":false,"stapler-class":"org.jenkinsci.plugins.postbuildscript.PostBuildScript","$class":"org.jenkinsci.plugins.postbuildscript.PostBuildScript"}
	at hudson.model.Descriptor.newInstance(Descriptor.java:600)
	at hudson.model.Descriptor.newInstancesFromHeteroList(Descriptor.java:1055)
	at hudson.model.Descriptor.newInstancesFromHeteroList(Descriptor.java:1017)
	at hudson.util.DescribableList.rebuildHetero(DescribableList.java:208)
	at hudson.model.Project.submit(Project.java:231)
	at hudson.model.Job.doConfigSubmit(Job.java:1354)
	at hudson.model.AbstractProject.doConfigSubmit(AbstractProject.java:771)
	at java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:627)
	at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:343)
	at org.kohsuke.stapler.interceptor.RequirePOST$Processor.invoke(RequirePOST.java:52)
	at org.kohsuke.stapler.PreInvokeInterceptedFunction.invoke(PreInvokeInterceptedFunction.java:26)
	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:129)
	at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
Caused: javax.servlet.ServletException
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:765)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
	at org.kohsuke.stapler.MetaClass$5.doDispatch(MetaClass.java:248)
	at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
	at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
	at org.kohsuke.stapler.Stapler.invoke(Stapler.java:649)
	at org.kohsuke.stapler.Stapler.service(Stapler.java:238)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:135)
	at org.jenkinsci.plugins.ssegateway.Endpoint$SSEListenChannelFilter.doFilter(Endpoint.java:225)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
	at io.jenkins.blueocean.ResourceCacheControl.doFilter(ResourceCacheControl.java:134)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
	at io.jenkins.blueocean.auth.jwt.impl.JwtAuthenticationFilter.doFilter(JwtAuthenticationFilter.java:61)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
	at com.smartcodeltd.jenkinsci.plugin.assetbundler.filters.LessCSS.doFilter(LessCSS.java:47)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
	at hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:95)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
	at hudson.plugins.greenballs.GreenBallFilter.doFilter(GreenBallFilter.java:59)
	at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
	at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:138)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:85)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	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:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:82)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:71)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:614)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)