Fix download log and remove log button display checks

For some reason when we run get('build.jobs.firstObject.id') it returns
different result than get('build.jobs').objectAt(0).get('id'). I can't reproduce
it on a clean Ember application, so it's probably a consequence of something
that we do in our views.

assets/scripts/app/templates/repos/show/actions.hbs

@@ -32,13 +32,17 @@
         {{/if}}
       </li>
     {{/if}}
-    {{!TODO: for some reason showDownloadLog, which just delegates to jobIdForLog
+    {{#if view.showDownloadLog}}
-             does not refresh 'if' properly, need further investigation}}
-    {{#if view.jobIdForLog}}
       <li class="icon download-log" title="Download Log">
         <a class="download-log" {{bind-attr href="view.plainTextLogUrl"}}></a>
       </li>
     {{/if}}
+    {{#if view.displayRemoveLog}}
+      <li class="icon remove-log" title="Remove Log">
+        <a href="#" {{action "removeLog" target="view"}}
+          {{bind-attr class="view.canRemoveLog::disabled"}}></a>
+      </li>
+    {{/if}}
     {{#if view.displayCodeClimate}}
       <li class="icon code-climate" title="Test Coverage with Code Climate">
         <a href="#" name="code-climate"

assets/scripts/app/views/repo/show.coffee

@@ -260,7 +260,7 @@ Travis.reopen
 
     jobIdForLog: (->
       @get('job.id') ||
-        (@get('build.jobs.length') == 1 && @get('build.jobs.firstObject.id'))
+        (@get('build.jobs.length') == 1 && @get('build.jobs').objectAt(0).get?('id'))
     ).property('job.id', 'build.jobs.firstObject.id', 'build.jobs.length')
 
     job: (->
@@ -283,7 +283,8 @@ Travis.reopen
     ).property('displayRemoveLog', 'hasPermission')
 
     displayRemoveLog: (->
-      (@get('isJobTab') || (@get('isBuildTab') && @get('build.jobs.length') == 1)) && @get('build.jobs.firstObject.canRemoveLog')
+      (@get('isJobTab') || (@get('isBuildTab') && @get('build.jobs.length') == 1)) &&
+        @get('build.jobs').objectAt(0).get?('canRemoveLog')
     ).property('isJobTab', 'isBuildTab', 'build.jobs.length', 'job.canRemoveLog')
 
     canCancelBuild: (->