I have only one customer which is me. I tried to edit the name and I get redirected to the startpage of the backend and the error `PHP Fatal error: Call to a member function setAttribute() on boolean in /srv/www/vhosts/hausfux/app/code/core/Mage/Eav/Model/Attribute/Data.php on line 80` is logged.

This is the line: `$dataModel->setAttribute($attribute);`

I logged $attribute and get this:

```
[_oldFieldsMap:protected] => Array
    (
    )

[_syncFieldsMap:protected] => Array
    (
    )

```

Im not sure what causes this error and how to solve it, please help.