作业列表：没有作业时下拉框被点击后，显示一条记录：目前尚未发布作业

app/views/homework_common/index.html.erb

@@ -45,11 +45,15 @@
         <li>
           <a href="javascript:void(0);" class="menu_arrow" style="font-size:16px; color:#4b4b4b; font-weight: normal; padding-left: 0px;">作业</a>
           <ul style="max-height:240px; overflow-y:auto; overflow-x:hidden;">
-            <% @homework_commons.each_with_index do |homework_common,index |%>
-                <li class="pr10">
-                  <%= link_to "作业#{@homework_commons.count - index}：#{homework_common.name}",student_work_index_path(:homework => homework_common.id),:target=>"_blank"%>
-                </li>
-            <% end%>
+            <% if @homework_commons.empty? %>
+                <li class="pr10" style="font-weight: normal; color: #888888; width: 120px; padding-left: 15px; padding-bottom: 5px;">目前尚未发布作业</li>
+            <% else %>
+                <% @homework_commons.each_with_index do |homework_common,index |%>
+                    <li class="pr10">
+                      <%= link_to "作业#{@homework_commons.count - index}：#{homework_common.name}",student_work_index_path(:homework => homework_common.id),:target=>"_blank"%>
+                    </li>
+                <% end%>
+            <% end %>
           </ul>
         </li>
       </ul>