Validation fails when parent role has no variable in inventory

Given the following playbook:

---
- name: test
  hosts: localhost
  gather_facts: true
  roles:
    - role: foobar
      tags:
        - foobar

Role foobar has foobar_variable_schema set with:

# tasks/main.yaml
---
- name: Import_role | validate role parameters
  ansible.builtin.import_role:
    name: validate_role_parameters
# vars/main.yaml
---
foobar_variable_schema:
  $schema: https://json-schema.org/draft-07/schema
  type: object
  properties:
    foobar_string:
      type: string
  required:
    - foobar_string

If foobar_string has no default value and is not set in inventory, task Validate | ensure role variables are properly defined fails:

TASK [validate_role_parameters : Validate | ensure role variables are properly defined] *******
fatal: [localhost]: FAILED! =>
  msg: |-
    The task includes an option with an undefined variable. The error was: 'validate_role_parameter_parent_variable' is undefined. 'validate_role_parameter_parent_variable' is undefined

    The error appears to be in '/SOME_PATH/role/validate_role_parameters/tasks/validate.yaml': line 35, column 3, but may
    be elsewhere in the file depending on the exact syntax problem.

    The offending line appears to be:


    - name: Validate | ensure role variables are properly defined
      ^ here