PHP Fatal error: Cannot use empty array elements in arrays

revision 1eb8754c24331dd6633acaf93f7aadcda3843e02

Message on PHP 7.1:

PHP Fatal error: Cannot use empty array elements in arrays in file.php on line 1

Happens when there are two consecutive commas: [1,,2]

<?php
$a = array(
    1,
    ,
    2
);
?>