fixed NPE when no build has run yet.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@1727 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/model/Job.java

@@ -32,6 +32,7 @@ import org.kohsuke.stapler.StaplerRequest;
 import org.kohsuke.stapler.StaplerResponse;
 
 import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletResponse;
 import java.awt.Color;
 import java.awt.Paint;
 import java.io.File;
@@ -558,6 +559,10 @@ public abstract class Job<JobT extends Job<JobT,RunT>, RunT extends Run<JobT,Run
      * Returns the graph that shows how long each build took.
      */
     public void doBuildTimeGraph( StaplerRequest req, StaplerResponse rsp ) throws IOException {
+        if(getLastBuild()==null) {
+            rsp.setStatus(HttpServletResponse.SC_NOT_FOUND);
+            return;
+        }
         if(req.checkIfModified(getLastBuild().getTimestamp(),rsp))
             return;
         ChartUtil.generateGraph(req,rsp, createBuildTimeTrendChart(),500,400);
@@ -568,6 +573,10 @@ public abstract class Job<JobT extends Job<JobT,RunT>, RunT extends Run<JobT,Run
      * Loaded lazily by AJAX.
      */
     public void doBuildTimeGraphMap( StaplerRequest req, StaplerResponse rsp ) throws IOException {
+        if(getLastBuild()==null) {
+            rsp.setStatus(HttpServletResponse.SC_NOT_FOUND);
+            return;
+        }
         if(req.checkIfModified(getLastBuild().getTimestamp(),rsp))
             return;
         ChartUtil.generateClickableMap(req,rsp, createBuildTimeTrendChart(),500,400);

core/src/main/resources/hudson/model/Job/buildTimeTrend.jelly

@@ -3,6 +3,8 @@
   <l:layout title="Build time trend">
 		<st:include page="sidepanel.jelly" />
 		<l:main-panel>
+      <j:choose>
+        <j:when test="${it.builds.size()&gt;1">
           <div align="center">
             <img src="buildTimeGraph" width="500" height="400" lazymap="buildTimeGraphMap"/>
           </div>
@@ -34,6 +36,11 @@
               </j:forEach>
             </table>
           </div>
+        </j:when>
+        <j:otherwise>
+          More than 1 builds are needed for the trend report.
+        </j:otherwise>
+      </j:choose>
     </l:main-panel>
 	</l:layout>
 </j:jelly>
\ No newline at end of file