Fix behavior of eth_getTransactionHash for pending transactions (ethe…

…reum#1217)

* Fix eth_getTransactionReceipt

* fix behavior of GetTransactionReceipt

* align logix exactly to upstream

internal/ethapi/api.go

@@ -1326,8 +1326,8 @@ func (s *PublicTransactionPoolAPI) GetRawTransactionByHash(ctx context.Context,
 // GetTransactionReceipt returns the transaction receipt for the given transaction hash.
 func (s *PublicTransactionPoolAPI) GetTransactionReceipt(ctx context.Context, hash common.Hash) (map[string]interface{}, error) {
 	tx, blockHash, blockNumber, index, err := s.b.GetTransaction(ctx, hash)
-	if err != nil || tx == nil {
-		return nil, err
+	if err != nil {
+		return nil, nil
 	}
 	receipts, err := s.b.GetReceipts(ctx, blockHash)
 	if err != nil {