Image not updating after undo/redo

Found that if I hit Undo and removed the last layer in an image (returning it to a blank canvas), and then Redo to return the layer, the image does not update until some other action is performed (scroll in/out, lock/unlock image, etc).

To recreate:

1. Create a new, empty image record
2. Add an asset as a new layer - e.g. Forest_background_25x25.jpg
3. Hit Ctrl+Z to undo which removes the layer (now empty image is grey instead of returning to default white)
4. Hit Ctrl+Y to redo which re-adds the layer but it is not visible (image remains grey)
5. Scroll mousewheel or lock/unlock image to make the layer visible again

[TEST] v4.1.5 (2021-08-13)
5E v2021-07-06

Users always try things devs never think about. Hence the value of open beta testing :)