PHP notice in `theme status` when theme name is not passed

`wp theme status`

Output:

`
PHP Notice:  Undefined offset: 0 in /home/nilambar/personal/gitarea/wp-cli/php/commands/theme.php on line 82
Notice: Undefined offset: 0 in /home/nilambar/personal/gitarea/wp-cli/php/commands/theme.php on line 82
`
