fix css display issue && fix export school report error

app/views/managements/schools/_data_contrast_list.html.erb

@@ -6,9 +6,12 @@
                  options_for_select(@select_options, params[:contrast_column]),
                  class: 'fl task-height-30 contrast-column-select',
                  style: 'position: absolute; right: 30px; top: 15px;' %>
-  <div style="position: absolute; left: 20px; bottom: 15px;">
-    说明：新增数=时段二-时段一；新增百分比=(新增数/时段一)*100%(保留小数点后五位)
-  </div>
+
+  <% if @obj_count.nonzero? %>
+    <div style="position: absolute; left: 20px; bottom: 0; font-size: 12px;">
+      说明：新增数=时段二-时段一；新增百分比=(新增数/时段一)*100%(保留小数点后五位)
+    </div>
+  <% end %>
 </div>
 
 <% if @obj_count.nonzero? %>

app/views/managements/schools/statistics.html.erb

@@ -39,7 +39,7 @@
   function exportSchoolStatistic(){
     var form = $("#school_report_search_form")
     var exportLink = form.find(".export-statistic-btn");
-    var keyword = form.find("input[name='keyword'").val();
-    exportLink.attr("href", exportLink.attr("href") + "?keyword=" + keyword);
+    var keyword = form.find("input[name='keyword']").val();
+    exportLink.attr("href", exportLink.attr("href").split('?')[0] + "?keyword=" + keyword);
   }
 </script>