grease pencil material preview thumbnails in 4.1 are bugged

It is a minor issue, and I could not find where to submit this on the developer forum.

In 4.1 when you create a NEW material, the preview thumbnail has a checkered background rather than a transparent background.

The materials listed above material.015 are from a file created with 4.0, so their backgrounds remain transparent.

the reason this is an issue is the checkered thumbnail bg makes the color less readable.

I was able to repeat the issue in the current 4.2 release but not reliably.