A custom grid has been running and working on a website I now do the support for.
The only thing that hasn't been working is when you click on any filter the page loads without much styling.
I have been tasked to find out what's wrong and to solve it but I'm at a loss.
I've found out that I get the error below
I've tried doing a require_once on the grid.js file (src/js/mage/adminhtml/grid.js), where varienGrid is declared, in the Grid.php file that creates the custom grid, but that didn't help as it just shut my website down because it claims to not being able to find the file.
So the question is
Does anybody have any idea how to solve this?
I'm rather sure my path to the file was correct but it could be that I'm wrong.