Created attachment 145343 [details]
EmptySpaceFillIssue

SUMMARY
Krita git hash is 6db92d4.

There's like an issue with weirdly filled blank space which occurs in two cases.

STEPS TO REPRODUCE
Case 1 : Using Eraser on blank space
1.1. select an eraser brush or activate the erase mode 
1.2. erase in an already blank or empty area on a layer.

Case 2 : with opaque pixel data on a layer
2.1. Paint a little shape on a new layer
2.2. Flip the painted data left, right, up, down


OBSERVED RESULT
Case 1 : blank space is filled in the layer thumbnail
Case 2 : Krita "abnormally" fills the empty space travelled by the pixel data on the layer,
unnecessarily causing memory use. It result in a big rect shape with tiny pixel data in it.
Use transform tool to verify.


EXPECTED RESULT
Empty layer should be empty and not behave like it's filled, be it
on the layer thumbnail, or with the layer pixel data itself.

Warning : Might want to check whether it's happening with vector layers too.
Also this issue might've been hidden and present in many previous versions and current versions.


SOFTWARE/OS VERSIONS
Windows : 10 21H1