[Bug] VAE Decode (Tiled) shifts color and contrast on images

This is an issue I noticed when using img2img to upscale and add detail to generated images. When either I manually add a `VAE Decode (Tiled)` node, or when the normal `VAE Decode` node hits a VRAM limit and automatically switches to a tiled mode, the resulting image will have a very noticiable shift in both saturation and contrast. See examples below (first is mine, second is from fellow user mxRoot):

Before | After
:-------------------------:|:-------------------------:
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To further test how this effect may compond over multiple uses of this node, I created a workflow that would take an image from a file and run it through a chain of 9 pairs of encode and decode nodes on each combination (normal+normal, normal+tiled, tiled+normal, tiled+tiled). You can find the JSON for the workflow on the link below if you want to run the test yourself:

https://pastebin.pl/view/044d18da


Here is the original image I created for the test:


And here is an example of the resulting images after completing each chain: