3.1.23 - Foreach in foreach issue

[Naki]

Example template data:

$data = [
    'rows' => [[], ['children' => ['bug appears here']], []]
];

Example template file:

{foreach $rows as $row}
    {$row@index}, 
    {if !empty($row.children)}
        {foreach $row.children as $children}
            {* anything *}
        {/foreach}
    {/if}
{/foreach}

Output:
0, 1, 1,

Should be:
0, 1, 2,

[uwetews]

This is now fixed in dev-master