It appears to be a problem with the performDatabaseCheck method. If you disable the Database Check option, the error should go away. I would assume that you get the same errors if you try the Database Check, Repair, or Optimize feature because they are all very similar. Is it possible that you do not have proper permissions in MySQL to perform a "SHOW TABLE STATUS" query?
As far as your backup files go, It does not appear that the error messages will effect the backup file, however you should still double check that the backup files are being created properly.
Thanks!