修改管理员界面作业列表报500错误的bug

app/views/admin/homework.html.erb

@@ -37,9 +37,11 @@
             <td style="white-space: nowrap;overflow: hidden;text-overflow: ellipsis;" class="name" title='<%=homework.name%>'>
               <%=link_to(homework.name, student_work_index_path(:homework => homework.id))%>
             </td>
+            <% if homework.course %>
             <td style="white-space: nowrap;overflow: hidden;text-overflow: ellipsis;" class="name" title='<%=homework.course.name%>'>
               <%= link_to(homework.course.name, course_path(homework.course.id)) %>
             </td>
+            <% end %>
             <td align="center" style="white-space: nowrap;overflow: hidden;text-overflow: ellipsis;" class="name" title='<% if homework.try(:user).try(:realname) == ' '%><%= homework.try(:user)%><% else %><%=homework.try(:user).try(:realname) %><% end %>'>
               <% if homework.try(:user).try(:realname) == ' '%>
                   <%= link_to(homework.try(:user), user_path(homework.user_id)) %>