Wrong Scale of Thumbnail Previews in Auto Zoom mode when disabling EnableGalleryShellThumbnail

[Shingedo]

Windows OS version

Windows 11 25H2

ImageGlass version

ImageGlass_10.0.2.66

ImageGlass release

Classic

1️⃣ Steps to reproduce

1. Set "EnableGalleryShellThumbnail" to false and clear thumbnail cache
2. Set Zoom to "Auto zoom"
3. Switch to an image whose full resolution is smaller than the full view canvas (in my case a 2500x1667 image on a 4K Monitor)

2️⃣ Actual behavior

The preview thumbnail is show very small (at 100% of the thumbnail size) in the center of the canvas until the full image is loaded.

3️⃣ Expected behavior

The thumbnail preview should be scaled up to fill the original image dimenstion.
This works correctly for images that are greater than the canvas size, but somehow fails for ones that are smaller.

4️⃣ Screenshots / Video / Sample image file

No response

5️⃣ Additional context

Edit: This also happens in a slide show