PERCH FORMS html code in 'code_block.html' template

I wish to allow my client to update a simple form on their website without coming to me to update the form.html file. I was going to do this by creating a region and pasting in the full 'form.html' template html so they can edit the form's code when they need to add a new item etc.

The form display's fine on the site but when submitted it shows the following message in the browser:

Fatal error: Call to a member function label() on a non-object in /home/hostingname/public_html/clientname/perch/addons/apps/perch_forms/runtime.php on line 25

Does anyone have any solutions to this?