xml - PdfHelper return Object reference not set to an instance on Umbraco 7.4 -

i have installed pdf creator on umbraco 7.4. if test using razor example template, can create pdf when using pdfhelper returns

system.nullreferenceexception: object reference not set instance of object.  line 3:  @helper start() { line 4:      <!-- start root --> line 5:         @html.raw("<fo:root xmlns:fo=\"http://www.w3.org/1999/xsl/format\" xmlns:ibex=\"http://www.xmlpdf.com/2003/ibex/format\">") line 6:      <!-- end root --> line 7:  } 

i have created new template:

<?xml version="1.0" encoding="utf-8" ?> @inherits umbraco.web.mvc.umbracotemplatepage  @{     layout = null;     //response.contenttype = "text/xsl";     //response.appendheader("x-pdf-render", "true");      // -- uncomment force browser download pdf.     // response.appendheader("x-pdf-force-download","darren.pdf"); }   @pdfhelper.start()      @pdfhelper.metadata(@currentpage.name, "darren ferguson")     @pdfhelper.layouttwocolumna4()       @* ecnryption , password protection there a:        pdfhelper.secure() , pdfhelper.secure("userpass", "ownerpass") helper *@      @pdfhelper.startbody()         @pdfhelper.startarea("header")           @pdfhelper.block(@currentpage.name, "arial", "23pt", "#3399ff")        @pdfhelper.endarea()         @pdfhelper.startarea("body")            @pdf.renderrichtext(@currentpage.bodytext)            @pdfhelper.pagerblock()         @pdfhelper.endarea()      @pdfhelper.endbody()     @pdfhelper.end() 

and returns above mentioned error.

the log file contains this:

 2016-04-19 08:42:41,711 [p16524/d23/t130] error umbraco.core.umbracoapplicationbase - unhandled exception occurred system.nullreferenceexception: object reference not set instance of object.    @ asp.pdfhelper.<start>b__0(textwriter __razor_helper_writer) in c:\development\projects\support\support\app_code\pdfhelper.cshtml:line 5    @ system.web.webpages.webpagebase.write(helperresult result)    @ asp._page_views_pdf_cshtml.execute() in c:\development\projects\support\support\views\pdf.cshtml:line 12    @ system.web.webpages.webpagebase.executepagehierarchy()    @ system.web.mvc.webviewpage.executepagehierarchy()    @ system.web.webpages.webpagebase.executepagehierarchy(webpagecontext pagecontext, textwriter writer, webpagerenderingbase startpage)    @ umbraco.core.profiling.profilingview.render(viewcontext viewcontext, textwriter writer)    @ system.web.mvc.viewresultbase.executeresult(controllercontext context)    @ system.web.mvc.controlleractioninvoker.invokeactionresultfilterrecursive(ilist`1 filters, int32 filterindex, resultexecutingcontext precontext, controllercontext controllercontext, actionresult actionresult)    @ system.web.mvc.controlleractioninvoker.invokeactionresultfilterrecursive(ilist`1 filters, int32 filterindex, resultexecutingcontext precontext, controllercontext controllercontext, actionresult actionresult)    @ system.web.mvc.controlleractioninvoker.invokeactionresultfilterrecursive(ilist`1 filters, int32 filterindex, resultexecutingcontext precontext, controllercontext controllercontext, actionresult actionresult)    @ system.web.mvc.controlleractioninvoker.invokeactionresultfilterrecursive(ilist`1 filters, int32 filterindex, resultexecutingcontext precontext, controllercontext controllercontext, actionresult actionresult)    @ system.web.mvc.controlleractioninvoker.invokeactionresultwithfilters(controllercontext controllercontext, ilist`1 filters, actionresult actionresult)    @ system.web.mvc.async.asynccontrolleractioninvoker.<>c__displayclass21.<begininvokeaction>b__1e(iasyncresult asyncresult)    @ system.web.mvc.async.asynccontrolleractioninvoker.endinvokeaction(iasyncresult asyncresult)    @ system.web.mvc.controller.<beginexecutecore>b__1d(iasyncresult asyncresult, executecorestate innerstate)    @ system.web.mvc.async.asyncresultwrapper.wrappedasyncvoid`1.callenddelegate(iasyncresult asyncresult)    @ system.web.mvc.controller.endexecutecore(iasyncresult asyncresult)    @ system.web.mvc.async.asyncresultwrapper.wrappedasyncvoid`1.callenddelegate(iasyncresult asyncresult)    @ system.web.mvc.controller.endexecute(iasyncresult asyncresult)    @ system.web.mvc.mvchandler.<beginprocessrequest>b__5(iasyncresult asyncresult, processrequeststate innerstate)    @ system.web.mvc.async.asyncresultwrapper.wrappedasyncvoid`1.callenddelegate(iasyncresult asyncresult)    @ system.web.mvc.mvchandler.endprocessrequest(iasyncresult asyncresult)    @ system.web.httpapplication.callhandlerexecutionstep.system.web.httpapplication.iexecutionstep.execute()    @ system.web.httpapplication.executestep(iexecutionstep step, boolean& completedsynchronously) 

problem fixed using template