Bitcoin-Qt: prevent stuck/unusable debug window on exit

- when closing the client with an open debug window, that window could
  become stuck/unsuable (it was still shown wherea the main window was
  hidden already)
- fix this by hiding the debug window, when quitting the the client

src/qt/bitcoingui.cpp

@@ -157,6 +157,8 @@ BitcoinGUI::BitcoinGUI(bool fIsTestnet, QWidget *parent) :
 
     rpcConsole = new RPCConsole(this);
     connect(openRPCConsoleAction, SIGNAL(triggered()), rpcConsole, SLOT(show()));
+    // prevents an oben debug window from becoming stuck/unusable on client shutdown
+    connect(quitAction, SIGNAL(triggered()), rpcConsole, SLOT(hide()));
 
     // Install event filter to be able to catch status tip events (QEvent::StatusTip)
     this->installEventFilter(this);