[Qt] use BitcoinGUI::DEFAULT_WALLET constant in bitcoin.cpp

src/qt/bitcoin.cpp

@@ -414,8 +414,8 @@ void BitcoinApplication::initializeResult(int retval)
         {
             walletModel = new WalletModel(pwalletMain, optionsModel);
 
-            window->addWallet("~Default", walletModel);
+            window->addWallet(BitcoinGUI::DEFAULT_WALLET, walletModel);
-            window->setCurrentWallet("~Default");
+            window->setCurrentWallet(BitcoinGUI::DEFAULT_WALLET);
 
             connect(walletModel, SIGNAL(coinsSent(CWallet*,SendCoinsRecipient,QByteArray)),
                              paymentServer, SLOT(fetchPaymentACK(CWallet*,const SendCoinsRecipient&,QByteArray)));