Fix message given when applying a disabled template with low security account.

Listing templates from security 0 account with default config:
```
2 (whatever)
4 (whatever the sequel)
```
Templates 1 and 3 are added, but are invisible to this player due to conf settings. Trying to apply these settings will give the error message "This template is disabled." and trying to apply a template of index 12 or something will say "This template has not been added." In situations like this, the player should instead see something like "This template is unavailable."