WC_Customer() class not working

When I am logged in as a user on my woocommerce website and I try to create a new WC_Customer, I get a fatal error telling me:

"Call to a member function get() on null"

I have tried to do this with a plugin as well as in the functions.php file of my theme, with the same result.

This is the line provoking the error, in the WC_Customer class:

$this->_data = (array) WC()->session->get( 'customer' );

Note: The website is still running locally

via Chebli Mohamed