修改《关于添加分班的问题：老师添加分班成功后，再次添加分班时输入框中记录的是上次分班名称》bug

Signed-off-by: alan <547533434@qq.com>

app/views/courses/_groups_name.html.erb

@@ -20,7 +20,7 @@
             %>
         <% end %>
         <% if @canShowCode %>
-        <a href="javascript:void(0)" class="f_l" onclick="$('#add_tag_<%= group.id %>').slideToggle();"><img src="/images/pic_edit.png" width="14" height="15" alt="编辑班级" /></a>
+        <a href="javascript:void(0)" class="f_l" onclick="document.getElementById('group_name<%= group.id %>').value='';$('#add_tag_<%= group.id %>').slideToggle();"><img src="/images/pic_edit.png" width="14" height="15" alt="编辑班级" /></a>
         <% end %>
       </li>
       <li>
@@ -36,7 +36,7 @@
      <% end %>
       <% if @canShowCode %>
       <li style="margin-left:15px;">
-        <a href="javascript:void(0)" class="st_add f_l" onclick="$('#add_tag04').slideToggle();">+添加分班</a>
+        <a href="javascript:void(0)" class="st_add f_l" onclick="document.getElementById('group_name').value='';$('#add_tag04').slideToggle();">+添加分班</a>
       </li>
       <li>
         <span id="add_tag04" style="display:none; vertical-align: middle;" class="ml10 f_l">
@@ -44,7 +44,7 @@
 
                     <%= text_field_tag "group_name", params[:group_name], size: "20", class: "isTxt w90 f_l", style: "padding: 0px",  maxlength: "100" %>
                     <%= submit_tag '', class: "submit f_l",:onclick => "validate_add_group()", style: "width: 43px;height: 21px;background: url(/images/btn.png) no-repeat 0 0;" %>
-                    <%= link_to_function '', "$('#add_tag04').slideToggle();", class: "submit_2", style: "width: 43px"%>
+                    <%= link_to_function '', "document.getElementById('group_name').value='';$('#add_tag04').slideToggle();", class: "submit_2", style: "width: 43px"%>
 
        <% end %>
        </span>