增加教师功能用户打包下载所有作业的功能

app/controllers/zipdown_controller.rb

@@ -75,7 +75,9 @@ class ZipdownController < ApplicationController
     # 得到每一个人所有文件打包的zip文件
     # 并将每一个人的zip打包为一个并返回路径
     user_zip_paths = homeattaches.map do |homeattach|
-      zip_homework_by_user homeattach
+      if homeattach.attachments.count > 0
+        zip_homework_by_user homeattach
+      end
     end
     zipping "#{Time.now.to_i}_#{bid.name}.zip", user_zip_paths, OUTPUT_FOLDER
 

app/views/bids/_homework_list.html.erb

@@ -8,7 +8,7 @@
 	<table width="100%" valign="center">
 		<tr>
 			<td ><span style="margin-left:0px"><%= l(:label_task_plural)%>(<%= @homework_list.count%>)</span>
-        <%#= link_to "作业打包下载", zipdown_assort_path(obj_class: @bid.class, obj_id: @bid), remote: false, class: "button_submit button_submit_font_white", style: "margin: 5px 10px;line-height: 20px;height: 20px;display: inline-block;" if(is_teacher) %>
+        <%= link_to "作业打包下载", zipdown_assort_path(obj_class: @bid.class, obj_id: @bid), remote: false, class: "button_submit button_submit_font_white", style: "margin: 5px 10px;line-height: 20px;height: 20px;display: inline-block;" if(is_teacher && @bid.homeworks.count > 0) %>
             </td>
             <td align="right">
                 <div class="project-search">