diff PNG is missing IEND chunk/invalid CRC checksum

[jochen-testingbot]

Hi,

When using odiff 3.1.1 or lower, a PNG file is correctly generated showcasing the diff between two images:

./node_modules/.bin/odiff one.png two.png --diff-mask diff.png

However, the diff.png seems to be slightly corrupted. When I try to convert it to for example jpg, ImageMagick will complain:

convert diff.png diff.jpg

convert: Expected 8 bytes; found 0 bytes `diff.png' @ warning/png.c/MagickPNGWarningHandler/1526.
convert: Read Exception `diff.png' @ error/png.c/MagickPNGErrorHandler/1492.
convert: no images defined `diff.jpg' @ error/deprecate.c/ConvertImageCommand/3368.

The PNG shows up fine in my Chrome browser or on macOS.
When I try to inspect/repair through https://compress-or-die.com/repair it will repair the image and I can use it with ImageMagick.
The output from this is:

Added missing IEND chunk. Probably the image file was truncated and the IDAT chunk could also be incomplete.
--
Combined all IDAT chunks.
Fixed CRC checksum for chunk "IDAT".
Fixed CRC checksum for chunk "IEND".