Unable to set dynamic values to send email step in workflow

When I close the window I get this error every time

Microsoft Dynamics CRM Error Report Contents

<CrmScriptErrorReport>

 <ReportVersion>1.0</ReportVersion>

 <ScriptErrorDetails>

  <Message>Uncaught TypeError: Cannot read property '_events' of null</Message>

  <Line>0</Line>

  <URL>/_common/global.ashx?ver=1929410703</URL>

  <PageURL>/SFA/Workflow/entityform.aspx?appSolutionId=%7b10343AC9-04EC-E311-94C4-D781E538593D%7d&entityFullName=email&entityname=email&mode=2&primaryentity=contract&stepId=SendEmailStep1&workflowId=88fb9ae0-9f3c-46d5-8f01-852ec879a629</PageURL>

  <Function>anonymousr:Cannotreadproperty'_events'ofnull</Function>

  <CallStack>

   <Function>anonymousr:Cannotreadproperty'_events'ofnull</Function>

  </CallStack>

 </ScriptErrorDetails>

 <ClientInformation>

  <BrowserUserAgent>Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.114 Safari/537.36</BrowserUserAgent>

  <BrowserLanguage>undefined</BrowserLanguage>

  <SystemLanguage>undefined</SystemLanguage>

  <UserLanguage>undefined</UserLanguage>

  <ScreenResolution>1364x768</ScreenResolution>

  <ClientName>Web</ClientName>

  <ClientTime>2014-06-05T05:19:59</ClientTime>

 </ClientInformation>

 <ServerInformation>

   <OrgLanguage>1033</OrgLanguage>

   <OrgCulture>1033</OrgCulture>

   <UserLanguage>1033</UserLanguage>

   <UserCulture>1033</UserCulture>

   <CRMVersion>6.0.1.61</CRMVersion>

 </ServerInformation>

</CrmScriptErrorReport>Microsoft Dynamics CRM Error Report Contents

Can any please respond on how to fix this issue asap...