CMS admin part not working as expected

<%- if @topic_view.topic.tags.present? %>
<%= t 'js.tagging.tags' %>: <%- @topic_view.topic.tags.each do |t| %> <%= t %> <%- end %>
<% end %>

Silverstripe Version: Silverstripe 4.2

Question:
We’ve been upgrading to 4.2 lately and now we experience some problems which we cannot identify and thus need your help.

When we in the CMS admin add or delete DataObjects, we get a blank page, and that is frustrating to the users. Can you please help us identify and solve the problem?

Details of your query go here

// Include any relevant code. If you have a lot of code, link to a gist instead.

The first place to look is the server logs to see if any errors are being thrown.
Did you test the upgrade in a development environment first, or have you upgraded your production site directly? You may need to try putting the site in dev mode to see if there is any debugging information in the response.

Hi

We haven’t found any errors in the server log and yes we tested upgrade in a development environment first.

So, everything was fine in the dev environment?
Is your dev environment identical to the production server? (PHP versions, MySQL versions, etc.)

Generally, if there’s a blank screen, there should be an error being thrown somewhere. It may be that you need to turn up the error reporting on your production machine.