Coursepress Template gets warning array_key_exists()

Hi guys,
Trying to do my own template file for register a new user using the coursepress theme, I got to:
wp-content\plugins\coursepress\includes\templates and got the file:student-signup.php

So, I copied this file, and copied it to my template folder. Then, erased all the code at this and start to make my own form to register at the site.

all the coursepress template files use this structure:
- <?php get_head(); ?> at the top
- <?php get_footer(); ?> botom.

When add the get_head(); code, the Coursepress returns to me:
array_key_exists() expects parameter 2 to be array, null given in ..\wp-content\plugins\coursepress\includes\classes\class.shortcodes.php on line 2656

Here, attached there is the PHP Stack Trace to the error. The website is at my localhost, and can't allow anyone the access them.