webp files with transparency do not display correctly

[jeffmcneill]

 * Pix version 2.6.5
 * Distribution - LMDE 4

Issue When displaying .webp files with transparency, the transparency is not transparent, but has some colors from nearby pixels

Steps to reproduce

• Take a png file with transparency.
• Convert to webp (using cwebp or ImageMagick convert).
• View in Pix

Expected behaviour

• Should see the file with transparency just as with png

Actual behaviour

• Transparency is changed into colors from nearby pixels

Left side is the .png version and right side is the .webp version as displayed in Pix

(Cannot include the .webp image here because Github says "We don't support that file type."

Other information

[Rio517]

This is also an issue in:

• Pix version 2.8.4
• Distribution - Linux Mint Cinnamon 20.3