I deleted a User-Defined Field and the associated grid gives an error | v8+
User-Defined Fields can be associated to one or more tables of data. If you delete a user-defined field that has been associated to a table of data the grid will give an error when you try to access it.
You can fix this by editing the User-Defined field definition as follows:
Go to Administration > User-defined Fields
At the top right of the screen, click 'Manage'
In the pop up find the table of data on which you had the issue
Select it and click 'Edit'
Edit and or change the Sections and Fields
Click 'OK'
The grid should now load as expected.