fix rotation on flxfilterframes demo

[ninjamuffin99]

I believe in FlxFilterFrames.applyToSprite() function, it adds an offset (from this flixel merge/pr https://github.com/HaxeFlixel/flixel/pull/2176)

here we simply just reset the offset to the sprite, so it doesn't adjust the offset incorrectly and constantly increment it

[Geokureli]

so it seems the issue is that it adds the offset every frame, but it should only add the offset when the filter wasn't active previously?

[ninjamuffin99]

right, so could be something that's changed within flixel itself!

could also do something like account for it's current offset maybe. I'll leave the flixel side up to you though :)

[Geokureli]

I'm not entirely sure what the best course of action is here, I think FlxFilterFrames usefulness is highly situational, I don't think I would use it in the way this demo does, where it generates new frames every update, and I think it's mostly a leftover feature from flixel's blitting days. for most of these I would try to use a shader, but even that isn't a perfect solution

I've decided to merge this, and take a look at FlxFilterFrames to see if there's a way to un-apply the current effects before re-applying, but really this class might need a rewrite

[Geokureli]

Thanks!