set lsBuild and lfBuild.

core/src/main/resources/hudson/views/LastDurationColumn/column.jelly

@@ -23,6 +23,8 @@ THE SOFTWARE.
 -->
 
 <j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form" xmlns:i="jelly:fmt">
+      <j:set var="lsBuild" value="${job.lastSuccessfulBuild}"/>
+      <j:set var="lfBuild" value="${job.lastFailedBuild}"/>
       <td data="${lsBuild.duration ?: lfBuild.duration ?: '0'}">
           <j:choose>
               <j:when test="${lsBuild!=null}">