Description:
------------
When imagescale() is called with the $mode set to IMG_WEIGHTED4,
the operation always fails.

This has been reported against upstream libgd[1], but as PHP's
bundled libgd is affected as well, I'm forwarding the issue.

[1] <https://github.com/libgd/libgd/issues/328>


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

$src = imagecreatetruecolor(100, 100);
imagefilledrectangle($src, 0,0, 99,99, 0xFFFFFF);
$dst = imagescale($src, 200, 200, IMG_WEIGHTED4);
var_dump($dst != NULL);


Expected result:
----------------
bool(true)

Actual result:
--------------
bool(false)