Update index.html.erb

fix bugs of &

Author: PENGZhaoqing

app/views/courses/index.html.erb

@@ -34,7 +34,7 @@
                   <td><%= course.name %></td>
                   <td><%= course.credit %></td>
                   <td><%= course.exam_type %></td>
-                  <td><%= course.teacher&.name %></td>
+                  <td><%= course.teacher.name %></td>
 
                   <% if teacher_logged_in? %>
                       <td><%= link_to "编辑", edit_course_url(course), class: 'btn btn-xs btn-info' %></td>
@@ -56,4 +56,4 @@
       </div>
     </div>
   </div>
-</div>
+</div>