Strict warning: Only variables should be passed by reference in seotools_admin_setup()

Strict warning: Only variables should be passed by reference in seotools_admin_setup() (line 16 of C:\xampp\htdocs\..\sites\all\modules\seotools\seotools.setup.inc)

I have been seeing frequently from other modules as well.
Don't call render(drupal_get_form(...));

Instead do this:
$form = drupal_get_form('seotools_setup_' . $step .'_form');
$output = render($form);