[ase] Fix out-of-bounds write in AsepriteParser

[Frixuu]

This is something I've stumbled upon a while ago, but I have not come up with a better solution since then ¯\_(ツ)_/¯

This PR makes sure that the size of celWxcelH is not larger than one of the destination buffer frame.pixels.

[jeremyfa]

Thanks for the PR, but do you have an actual ase file example that reproduces the issue yoi are fixing?

[Frixuu]

Sure: repro.aseprite.zip

using ceramic.SpritePlugin;
public override function preload() {
    this.assets.addSprite("repro");
}

With this patch my game loads and runs fine as expected.
Without this patch:

malloc(): corrupted top size
zsh: IOT instruction (core dumped)

[jeremyfa]

Thanks for the repro example, I’ll take a look!

[jeremyfa]

Went through the changes again, they make sense so far so merging it. Will test that over the various projects that use ase to make sure nothing breaks anyway, thanks!