Database warning for Add New user in ACP
 

vBulletin 3.82

Admin CP | Users | Add new user

As soon as I click on that menu item, although the page displays apparently correctly, I get this message at the top of the page:

Code:
Warning: array_merge() [function.array-merge]: Argument #1 is not an array in [path]/admincp/user.php(545) : eval()'d code on line 11
This occurs before I even begin to enter any data.

I previously posted this as a bug but I'm told it's caused by a plug-in. Any idea what might be causing this?