Error notices when using `wp widget add`

```
salty-wordpress ➜  wordpress-trunk.dev  wp widget add recent-posts sidebar-1 --number="5"
PHP Notice:  Undefined index: title in /srv/www/wordpress-trunk.dev/wp-includes/default-widgets.php on line 597
```

Unfortunately, I don't think there's any way for us to know which settings a widget expects. We'll just need to suppress errors when we call `$widget->update( $dirty_options, $old_options )`