PrependClass(): Argument #1 ($attr) must be of type string, null given

PHPMaker General Discussion (PHPMaker)
1

I’m getting the following error at the list page of some tables:

\src\phpfn.php(6882): PHPMaker2025\MY_APPLICATION\PrependClass(): Argument #1 ($attr) must be of type string, null given, called in \src\ListOptions.php on line 470

Argument #1 is set in the previous line. Lines 469 and 470 are:

$class = $button->getAttribute('class');
PrependClass($class, 'btn btn-xs btn-link');

I get rid of the error manually changing line 469 to:

$class = $button->getAttribute('class') ?? '';