wallet: improve error logging for unsuccessful notification handling

If a block arrives while the wallet is rescanning, users would be shown
a log message that is confusing and not very helpful.

wallet/chainntfns.go

@@ -7,7 +7,6 @@ package wallet
 import (
 	"bytes"
 	"fmt"
-	"strings"
 	"time"
 
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
@@ -132,7 +131,7 @@ func (w *Wallet) handleChainNotifications() {
 				err = walletdb.Update(w.db, func(tx walletdb.ReadWriteTx) error {
 					return w.addRelevantTx(tx, n.TxRecord, n.Block)
 				})
-				notificationName = "recvtx/redeemingtx"
+				notificationName = "relevant transaction"
 			case chain.FilteredBlockConnected:
 				// Atomically update for the whole block.
 				if len(n.RelevantTxs) > 0 {
@@ -163,7 +162,7 @@ func (w *Wallet) handleChainNotifications() {
 				}
 			case *chain.RescanFinished:
 				err = catchUpHashes(w, chainClient, n.Height)
-				notificationName = "rescanprogress"
+				notificationName = "rescan finished"
 				w.SetChainSynced(true)
 				select {
 				case w.rescanNotifications <- n:
@@ -172,17 +171,24 @@ func (w *Wallet) handleChainNotifications() {
 				}
 			}
 			if err != nil {
-				// On out-of-sync blockconnected notifications, only
-				// send a debug message.
-				errStr := "Failed to process consensus server " +
-					"notification (name: `%s`, detail: `%v`)"
+				// If we received a block connected notification
+				// while rescanning, then we can ignore logging
+				// the error as we'll properly catch up once we
+				// process the RescanFinished notification.
 				if notificationName == "block connected" &&
-					strings.Contains(err.Error(),
-						"couldn't get hash from database") {
-					log.Debugf(errStr, notificationName, err)
-				} else {
-					log.Errorf(errStr, notificationName, err)
+					waddrmgr.IsError(err, waddrmgr.ErrBlockNotFound) &&
+					!w.ChainSynced() {
+
+					log.Debugf("Received block connected "+
+						"notification for height %v "+
+						"while rescanning",
+						n.(chain.BlockConnected).Height)
+					continue
 				}
+
+				log.Errorf("Unable to process chain backend "+
+					"%v notification: %v", notificationName,
+					err)
 			}
 		case <-w.quit:
 			return