fix: eth: cleanup error cases

1. Return an error on gas estimation failure instead of logging.
2. Return early when processing signed messages on failure instead of
continuing.

node/impl/full/eth.go

@@ -895,7 +895,7 @@ func (a *EthModule) EthEstimateGas(ctx context.Context, tx ethtypes.EthCall) (et
 
 	expectedGas, err := ethGasSearch(ctx, a.Chain, a.Stmgr, a.Mpool, msg, ts)
 	if err != nil {
-		log.Errorw("expected gas", "err", err)
+		return 0, xerrors.Errorf("gas search failed: %w", err)
 	}
 
 	return ethtypes.EthUint64(expectedGas), nil
@@ -2157,11 +2157,13 @@ func (m *EthTxHashManager) ProcessSignedMessage(ctx context.Context, msg *types.
 	ethTx, err := newEthTxFromSignedMessage(ctx, msg, m.StateAPI)
 	if err != nil {
 		log.Errorf("error converting filecoin message to eth tx: %s", err)
+		return
 	}
 
 	err = m.TransactionHashLookup.UpsertHash(ethTx.Hash, msg.Cid())
 	if err != nil {
 		log.Errorf("error inserting tx mapping to db: %s", err)
+		return
 	}
 }