reset address balances before updating unspents (#1707)

cw_bitcoin/lib/electrum_wallet.dart

@@ -1272,6 +1272,11 @@ abstract class ElectrumWalletBase
       });
     }
 
+    // Set the balance of all non-silent payment addresses to 0 before updating
+    walletAddresses.allAddresses.forEach((addr) {
+      if(addr is! BitcoinSilentPaymentAddressRecord) addr.balance = 0;
+    });
+
     await Future.wait(walletAddresses.allAddresses.map((address) async {
       updatedUnspentCoins.addAll(await fetchUnspent(address));
     }));