Jail pool selection can be skipped
Select Jails. On the first entry, the user is prompted to "Choose an existing ZFS Pool". (Change the prompt to "Choose a pool or dataset for jail storage". "ZFS" and "existing" are redundant.)
However, the user can click Activate without choosing a pool, and the Jails screen is shown. This should not be possible.
If there are no pools when the user clicks Jails, display a dialog saying "No pools exist. Jails cannot be created or managed until a pool is present for storing them."