OUT of memory -> 0x0 pixel - undo data

[DOS386]

When editing a large image with XN, it happens that the image simply disappears, and XN saves it as a 0 pixel by 0 pixel file. The original file is lost. Most likely this is due to running out of memory. If you cut several small pieces from the big image (doesn't need extra memory - except for undo), it "reliably" disappears after a given amount of edits, but the program doesn't crash.

BUG: most likely XN tries to hog memory, and checks whether it got the memory (like (malloc(blah)!=0), so far good). But if it doesn't get the memory, it destroys the image in memory (sets to 0x0 pixel), instead of refusing to complete, and throwing a suitable message.

Q: does XN backup the complete image for every edit? How many undo-backups does it keep?

SUGG: add [0] "disable saving undo-backups" option and [1] "clear existing undo-backups" possibility - this will allow to edit bigger images faster or at all.

Still the "0x0-pixel-problem" is a BUG, the optimal way to reproduce it reliably is low RAM (<= 512 MiB) and a small fixed-size swap file (<=128 MiB) (believe or not, I still use my good old 64 MiB laptop).

IIRC long ago I had reported bad behaviour on huge images in NC too, no undo here, still not able to deal reasonably with the fact that a memory allocation failed.