Fix -Database parameter in Backup-DbaDatabase call
Fix -Database parameter in Backup-DbaDatabase call

The call to backup the database to NUL got the database object
instead of the database name as -Database parameter.
This generated the following warning:
WARNING: [18:47:27][Backup-DbaDatabase] No databases match the request for backups
This fixes issue #6611

wsmelton/dbatools,kozloski/dbatools