Minor bug fixes. 4.2.1.

lib/bitcoin/bitcoin_mnemonic_is_incorrect_exception.dart

@@ -1,5 +1,5 @@
 class BitcoinMnemonicIsIncorrectException implements Exception {
   @override
   String toString() =>
-      'Bitcoin mnemonic has incorrect format. Mnemonic should contain 24 words separated by space.';
+      'Bitcoin mnemonic has incorrect format. Mnemonic should contain 12 or 24 words separated by space.';
 }

lib/bitcoin/electrum_transaction_history.dart

@@ -35,7 +35,7 @@ abstract class ElectrumTransactionHistoryBase
 
   @override
   void addMany(Map<String, ElectrumTransactionInfo> transactions) =>
-      this.transactions.addAll(transactions);
+      transactions.forEach((_, tx) => _updateOrInsert(tx));
 
   @override
   Future<void> save() async {

lib/entities/wallet_type.dart

@@ -71,7 +71,7 @@ String walletTypeToDisplayName(WalletType type) {
     case WalletType.bitcoin:
       return 'Bitcoin (Electrum)';
     case WalletType.litecoin:
-      return 'Litecoin';
+      return 'Litecoin (Electrum)';
     default:
       return '';
   }