Handle the exception if _extra_data(instance) is called on a missing instance
Handle the exception if _extra_data(instance) is called on a missing instance

Closes-Bug: #1926928
Change-Id: Ib782ff21770978ef09eb8b44abe115b730f7e7f9

openstack/trove-dashboard,openstack/trove-dashboard,openstack/trove-dashboard,openstack/trove-dashboard