new warning after installing 7.x-2.4

I just upgraded FPA to 7.x-2.4, and almost immediately got a warning:

Strict warning: Only variables should be passed by reference in theme_fpa_user_admin_permissions() (line 123 of /home/nj8j/public_html/sites/all/modules/fpa/fpa.theme.inc).

This is the problem line:

$first_permission_index = array_shift(element_children($form['checkboxes']));

The problem appears to be that we're passing array_shift the return from element_children instead of an actual array variable.

Easiest way to fix this is to put the element_children return in a variable, and pass the variable.

Patch attached.