Fix warning when compiling in OS X

src/qt/notificator.cpp

@@ -28,8 +28,10 @@
 #endif
 
 
+#ifdef USE_DBUS
 // https://wiki.ubuntu.com/NotificationDevelopmentGuidelines recommends at least 128
 const int FREEDESKTOP_NOTIFICATION_ICON_SIZE = 128;
+#endif
 
 Notificator::Notificator(const QString &programName, QSystemTrayIcon *trayicon, QWidget *parent) :
     QObject(parent),