fix account settings page with account notification roles

test plan:
* on the accounts settings page, add a global announcement
* should not return an error after refreshing

fixes #CNVS-16850

Change-Id: I33c80c7abb95590fc43555006ddd3cf2c502907b
Reviewed-on: https://gerrit.instructure.com/44326
Reviewed-by: Dan Minkevitch <dan@instructure.com>
Product-Review: Dan Minkevitch <dan@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>