ask module: add rescue ackknowledgement

vendor/built_in_modules/ask/app/views/panel/ask/front_end/ask_questions/create.js.erb

@@ -1,5 +1,5 @@
 <% if @ask_question.errors.empty? %>
-  $('#acknowledgement').html('<p><%= t('ask.save_success') %>!</p><p><%= @ask_acknowledgement.content %></p>');
+  $('#acknowledgement').html('<p><%= t('ask.save_success') %>!</p><p><%= @ask_acknowledgement.content rescue '' %></p>');
   $('html,body').scrollTop(0);
 <% else %>
   alert('<%= @ask_question.errors.full_messages.join('\n') %>');