fix block height and hash for unconfirmed transations in store

The Transaction Store sets block hash to `0...0` for unconfirmed transaction instead of `nil`. This code change makes sure not to override the nil value of `blockHash` in that case.

wallet/wallet.go

@@ -2441,7 +2441,7 @@ func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 	// because not all block headers are saved but when they are for SPV the
 	// db can be queried directly without this.
 	var blockHash *chainhash.Hash
-	var height int32 = -1
+	var endHeight int32 = -1
 	if txResult != nil && txResult.BlockHash != "" {
 		blockHash, err = chainhash.NewHashFromStr(txResult.BlockHash)
 		if err != nil {
@@ -2455,17 +2455,17 @@ func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 			if err != nil {
 				return nil, false, err
 			}
-			height = header.Height
+			bestHeight = header.Height
 		case *chain.BitcoindClient:
-			height, err = client.GetBlockHeight(blockHash)
+			bestHeight, err = client.GetBlockHeight(blockHash)
 			if err != nil {
 				return nil, false, err
 			}
 		}
 
 		// We know that the transaction definitively is in a specific
 		// block height and set both start and end height to it.
-		bestHeight = height
+		endHeight = bestHeight
 	}
 
 	// Populate with additional data if this transaction exists in the
@@ -2489,16 +2489,18 @@ func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 				// transaction and can return early.
 				if txHash.IsEqual(dbTx.Hash) {
 					summary, inDB = &dbTx, true
-					height = details[i].Block.Height
-					blockHash = &details[i].Block.Hash
+					if details[i].Block.Height != -1 {
+						bestHeight = details[i].Block.Height
+						blockHash = &details[i].Block.Hash
+					}
 					return true, nil
 				}
 			}
 			return false, nil
 		}
 
 		return w.TxStore.RangeTransactions(
-			txmgrNs, bestHeight, height, rangeFn,
+			txmgrNs, bestHeight, endHeight, rangeFn,
 		)
 	})
 	if err != nil {
@@ -2535,7 +2537,7 @@ func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 	default:
 		res.MinedTransaction = &Block{
 			Hash:         blockHash,
-			Height:       height,
+			Height:       bestHeight,
 			Timestamp:    summary.Timestamp,
 			Transactions: []TransactionSummary{*summary},
 		}