NERA

Just throwing my observing into this issue.
I got similar error because I did some customization at child theme function file ..
It seems the call functions have been changed with latest update (WooCommerce update)

“Uncaught Error: Call to a member function get_billing_country() on null in ”
once commented this snapit code, the admin panel works perfectly

This is a common issue with 5.2 update … just revert back temporarily and wait for a fix.

You can do a test copy of your site try to identify and solve the real cause of the problem.

Had same problem …. regenerate the permalink pages solve the problem