Create haven default node instead of loading from YAML (#544)

lib/entities/default_settings_migration.dart

@@ -417,8 +417,7 @@ Future<void> checkCurrentNodes(
   }
 
   if (currentHavenNodeServer == null) {
-    final nodes = await loadDefaultHavenNodes();
-    final node = nodes.first;
+    final node = Node(uri: havenDefaultNodeUri, type: WalletType.haven);
     await nodeSource.add(node);
     await sharedPreferences.setInt(
         PreferencesKey.currentHavenNodeIdKey, node.key as int);

lib/view_model/node_list/node_list_view_model.dart

@@ -50,6 +50,9 @@ abstract class NodeListViewModelBase with Store {
       case WalletType.litecoin:
         node = getLitecoinDefaultElectrumServer(nodes: _nodeSource)!;
         break;
+      case WalletType.haven:
+        node = getHavenDefaultNode(nodes: _nodeSource)!;
+        break;
       default:
         throw Exception('Unexpected wallet type: ${wallet.type}');
     }