Problematic implements

[Liao1]

1. Need to check if the instance exist before using it (will not record issues in fulfillment pallet, since this pallet will be removed)
   After the block has been initialized, each valid extrinsic is executed in order of transaction priority. Extrinsics must not cause a panic in the runtime logic or else the system becomes vulnerable to attacks where users can trigger computational execution without any punishment. --Substrate Developer Hub
   

   automata/pallets/attestor/src/lib.rs

   Lines 218 to 219 in 3b11d55

   	let mut attestor = <Attestors<T>>::get(&who);
   	attestor.url = url;