Adds a null check qualification to showing a base type

fixes CNVS-6758

test plan:
  - Go to the permissions page (/accounts/##/permissions)
  - Click on account roles
  - Add a custom role
  - No tooltip should show for the custom account role

Change-Id: Icc60b0139b5b87309639c40530172e571e74e47f
Reviewed-on: https://gerrit.instructure.com/39244
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: Cosme Salazar