added isset() to if clause to avert php notice error message
Merge branch 'notice_undefined_method_sveapaymentplan_969' into hotfix/2.3.1
fixed bad redirect route on ssn validation failure
Merge branch 'redirected_away_from_cart_on_ssn_validation_failure' into hotfix/2.3.1
fixed bad approach to ssn validation for fi, no individual
fixed bad approach to ssn validation for fi, no individual for paymentplan
propagated fix to other credentials and countries
Merge branch 'validation_of_ssn_fails_with_no_individual' into hotfix/2.3.1
Merge branch 'hotfix/2.3.1'