A simple code to reproduce the bug:

<?php

$not_an_array = 'string';
a_function($not_an_array);

function a_function(array $array)
{
// do something
}

echo 'The script has not been aborted?';
?>

The code generates E_RECOVERABLE_ERROR error (the mismatch of argument type). When xdebug is enabled the code is not aborted.