You can not sign away your rights. If you sign a document that said your company can just kill you, they still wouldn't have any right to kill you.
I'd like to see a citation of anyone making something in their free time that a company was able to steal from them based on some work contract. And if someone can find citations that it does indeed work this way where you live, don't just quit. Move away from what ever insane place you live that allows this kind of literal slavery.