Error adding field to quote.

I have just upgraded from 7.4.3 to 7.5.1.
When I use ‘studio’ to try and add a field to a quote, and when I click on any of the existing fields or the ‘Add Field’ button I get a pop-up with the following error :-

An error has occurred

Warning: Creating default object from empty value in /home/mark7h/public_html/crm/modules/ModuleBuilder/views/view.modulefield.php on line 154
{“east”:{“title”:“Edit Field”,“crumb”:"",“content”:"

Any idea what is wrong?

I have found this thread which contains a fix :-

Is this :-

a) A regression
b) Not the correct fix
c) Something else?