Blank png file extracted from .wz files

[qoire]

Hi again, sorry for bothering,
While extracting the .png files I've encountered a lot of instances where the extracted .png file was blank (no data). I've encountered similar output trying to extract files using maplelib. I was wondering if there was any insight to be learnt about why this is occurring.

Below is the two images I have extracted, from the same animation:
This is the blank .png extract:

And this is the extract with content:

The headers with height and width are all formatted correctly, it's just that the data is missing.

I used this .wz file (yes Map.wz is huge now):
https://mega.co.nz/#!tUlCiBaZ!xM-0-cnfmVq82tlN9q8u_3kWJVmdM-ngMKys2gyeEDU

and the paths of the two images being extracted are:
"DynamicObjectStateEffect.img/86301010X/open/hide/4" //blank
"DynamicObjectStateEffect.img/86301010X/open/hide/0" //working

[angelsl]

Not a bug.

The images themselves are actually blank.