TenantProvider throws NPE when listing tenants root tenant resource does not exist

The method
org.apache.sling.tenant.TenantProvider#getTenants

throws an NPE when the tenant root resource does not exists.
The tenant root resource is created if needed when creating a tenant (see org.apache.sling.tenant.internal.TenantProviderImpl#createTenantResource)

A workaround is to create a tenant and remove it.