What this PR does / why we need it?

This PR closes #1305.

Since no genesis transaction is allowed after #1454 merged:

• transactions_root should always be the default value RLP_NULL as a normal block.

  axon/core/consensus/src/engine.rs

  Lines 75 to 83 in 412e52a

  	let txs_root = if !txs.hashes.is_empty() {
  	TrieMerkle::from_iter(txs.hashes.iter().enumerate())
  	.root_hash()
  	.unwrap_or_else(|err| {
  	panic!("failed to calculate trie root hash for transactions since {err}")
  	})
  	} else {
  	RLP_NULL
  	};

• signed_txs_hash should always be the default value RLP_EMPTY_LIST as a normal block

  axon/core/consensus/src/engine.rs

  Line 115 in 412e52a

  signed_txs_hash: digest_signed_transactions(&signed_txs),

  
  

  axon/core/consensus/src/util.rs

  Lines 19 to 25 in 412e52a

  	pub fn digest_signed_transactions(stxs: &[SignedTransaction]) -> Hash {
  	if stxs.is_empty() {
  	RLP_EMPTY_LIST
  	} else {
  	Hasher::digest(rlp::encode_list(stxs))
  	}
  	}

• receipts_root should always be the default value RLP_NULL as a normal block.

  axon/core/executor/src/lib.rs

  Lines 188 to 196 in 412e52a

  	let receipt_root = if hashes.is_empty() {
  	RLP_NULL
  	} else {
  	TrieMerkle::from_iter(hashes.iter().enumerate())
  	.root_hash()
  	.unwrap_or_else(|err| {
  	panic!("failed to calculate trie root hash for receipts since {err}")
  	})
  	};

• log_bloom should always calculated from an empty logs vector.

  axon/protocol/src/types/block.rs

  Lines 132 to 136 in 412e52a

  	let logs = exec_resp
  	.tx_resp
  	.iter()
  	.map(|r| Bloom::from(BloomInput::Raw(rlp::encode_list(&r.logs).as_ref())))
  	.collect::<Vec<_>>();

  axon/protocol/src/types/block.rs

  Lines 145 to 147 in 412e52a

  	log_bloom: Bloom::from(BloomInput::Raw(
  	rlp::encode_list(&logs).as_ref(),
  	)),

  ⚠️ It's not same as Default::default().

  The Default::default() is all zeros, but for an empty logs vector, it's not.

  The difference is as following:

    0000000000000000000000000000000000000000000000000000000000000000
  - 0000000000000000000000000000000000000000000000000000000000000000
  + 0000000000000080000000000000000000000000000000000000000000000000
                  ^
  - 0000000000000000000000000000000000000000000000000000000000000000
  + 0000010000001000000000000000000000000000000000000000000000000000
         ^      ^
    0000000000000000000000000000000000000000000000000000000000000000
    0000000000000000000000000000000000000000000000000000000000000000
    0000000000000000000000000000000000000000000000000000000000000000
    0000000000000000000000000000000000000000000000000000000000000000
    0000000000000000000000000000000000000000000000000000000000000000

• gas_used should always be zero.

What is the impact of this PR?

No Breaking Change