课程主页，如课程资料数为0，则取消显示

app/views/welcome/_course_list.html.erb

@@ -25,8 +25,10 @@
             <%= link_to course.school.name.try(:gsub, /(.+)$/, '\1'), options={:action => 'course', :school_id => course.school.id}, html_options={:method => 'get'} %>
         <% end %>
         (<%= course.members.count %>人)
-        <%# files_count = course.attachments.count.to_s %>
+        <% files_count = course.attachments.count %>
-        (<%= link_to "#{course.attachments.count.to_s}份", course_files_path(course) %>资料)
+        <% if files_count > 0%>
+            (<%= link_to "#{files_count.to_s}份", course_files_path(course) %>资料)
+        <% end %>
       </div>
     </li>
 <% end %>