1, your worry is unnecessary. It is neither procedural nor legal for you to sign a blank sheet of paper. Don't worry if you say anything. I'm worried because I don't know what to do with your signature.

If you are worried, you can ask and see what is written on your blank signature paper. If you don't write anything, you can ask to tear it up. You can sign it after the police rewrite it. So there is nothing to worry about!