Safeguard against filling whole image
Description of the feature
I've been recently working with very big images (10k x 10k+) with multiple layers. It's easy to make a mistake when using fill tool and accidentally initiate filling of whole image. Not really a big deal in itself, because you can easily undo it, but the problem is that the operation takes extremely long time (also it crashes in the newest version in some cases).
There should be some way to avoid it, like, if GIMP detects that you are trying to fill more than 1000000 pixels, it would automatically cancel the operation. This of course should be optional, but would be really helpful to have this option.