Description:
------------
If the callback for readline_completion_function returns an empty array, php will segfault.

When running the example code, hit tab to fire the callback.

Test script:
---------------
<?php

readline_completion_function('readline_callback');

do
{
	$command = readline('> ');
	echo 'command: ' . $command . PHP_EOL;
} while ($command);

function readline_callback($command)
{
	return [];
}