Fix displaying pull request number on builds' list

Commit sometimes does not have information about pull request (probably
when payload is coming from pusher).

assets/scripts/app/templates/builds/list.hbs

@@ -45,7 +45,7 @@
           {{#if view.isPullRequestsList}}
             <td>
               <a {{bindAttr href="view.urlGithubPullRequest"}}>
-                #{{commit.pullRequestNumber}}
+                #{{pullRequestNumber}}
               </a>
             </td>
           {{/if}}