Add aditional check if wallet exists with special name

lib/core/wallet_creation_service.dart

@@ -1,6 +1,8 @@
 import 'package:cake_wallet/di.dart';
+import 'package:cw_core/wallet_info.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import 'package:hive/hive.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:cake_wallet/core/key_service.dart';
 import 'package:cw_core/wallet_base.dart';
@@ -14,7 +16,8 @@ class WalletCreationService {
       {WalletType initialType,
       this.secureStorage,
       this.keyService,
-      this.sharedPreferences})
+      this.sharedPreferences,
+      this.walletInfoSource})
       : type = initialType {
     if (type != null) {
       changeWalletType(type: type);
@@ -25,6 +28,7 @@ class WalletCreationService {
   final FlutterSecureStorage secureStorage;
   final SharedPreferences sharedPreferences;
   final KeyService keyService;
+  final Box<WalletInfo> walletInfoSource;
   WalletService _service;
 
   void changeWalletType({@required WalletType type}) {
@@ -32,7 +36,21 @@ class WalletCreationService {
     _service = getIt.get<WalletService>(param1: type);
   }
 
+  bool exists(String name) {
+    final walletName = name.toLowerCase();
+    return walletInfoSource
+      .values
+      .any((walletInfo) => walletInfo.name.toLowerCase() == walletName);
+  }
+
+  void checkIfExists(String name) {
+    if (exists(name)) {
+      throw Exception('Wallet with name ${name} already exists!');
+    }
+  }
+
   Future<WalletBase> create(WalletCredentials credentials) async {
+    checkIfExists(credentials.name);
     final password = generateWalletPassword(type);
     credentials.password = password;
     await keyService.saveWalletPassword(
@@ -41,6 +59,7 @@ class WalletCreationService {
   }
 
   Future<WalletBase> restoreFromKeys(WalletCredentials credentials) async {
+    checkIfExists(credentials.name);
     final password = generateWalletPassword(type);
     credentials.password = password;
     await keyService.saveWalletPassword(
@@ -49,6 +68,7 @@ class WalletCreationService {
   }
 
   Future<WalletBase> restoreFromSeed(WalletCredentials credentials) async {
+    checkIfExists(credentials.name);
     final password = generateWalletPassword(type);
     credentials.password = password;
     await keyService.saveWalletPassword(