OP: validate num_pub_rand in handle_public_randomness_commit()

[maurolacy]

@bap2pecs cloned issue babylonchain/babylon-contract#186 on 2024-06-23:

in FP, we will add logic in fast sync:

		for lastCommitStartHeight, val := range lastCommitPR {

			if endHeight > lastCommitStartHeight+val.NumPubRand-1 {

				return nil, nil

			}

		}

if both lastCommitStartHeight and val.NumPubRand is 0, integer underflow can happen.

but in reality, we shouldn't allow NumPubRand to be 0. it should at least have 1 pubrand.

we should enforce this check in the CW contract

[maurolacy]

@bap2pecs commented on 2024-07-08:

closing for https://www.github.com/babylonchain/pm-integration/issues/5