Prevent warnings in PHP 8.2 when `$col_values` is empty

[danielbachhuber]

Fixes https://github.com/wp-cli/php-cli-tools/issues/159

Note: you'll need to resize your browser window in order to trigger the error warnings.

$  wp post create --post_title="Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tem por por por"
$ wp post list