Stop generating block if consensus cannot make a seal

If Tendermint consensus received an outdated block request, it returns
empty seal. Miner should stop the block generation if the seal is empty.

Author: majecty

core/src/miner/miner.rs

@@ -43,7 +43,7 @@ use crate::client::{
 };
 use crate::codechain_machine::CodeChainMachine;
 use crate::consensus::{CodeChainEngine, EngineType};
-use crate::error::Error;
+use crate::error::{BlockError, Error};
 use crate::scheme::Scheme;
 use crate::transaction::{PendingSignedTransactions, SignedTransaction, UnverifiedTransaction};
 use crate::types::{BlockId, TransactionId};
@@ -491,7 +491,7 @@ impl Miner {
             if let Some(seal_bytes) = seal.seal_fields() {
                 open_block.seal(self.engine.borrow(), seal_bytes).expect("Sealing always success");
             } else {
-                panic!("Seal should not be none")
+                return Err(BlockError::InvalidSeal.into())
             }
         }