message: qt: Fix missing qRegisterMetaType for size_t
  It is required in order to use size_t in QueuedConnections.
  Github-Pull:
  Rebased-From:
  Tree-SHA512:
diff: @@ -447,6 +447,7 @@ int GuiMain(int argc, char* argv[])
  // Need to pass name here as CAmount is a typedef (see http://qt-project.org/doc/qt-5/qmetatype.html#qRegisterMetaType)
  // IMPORTANT if it is no longer a typedef use the normal variant above
  qRegisterMetaType< CAmount >("CAmount");
  + qRegisterMetaType<size_t>("size_t");
  qRegisterMetaType< std::function<void()> >("std::function<void()>");
  qRegisterMetaType<QMessageBox::Icon>("QMessageBox::Icon");
  /// 2. Parse command-line options. We do this after qt in order to show an error if there are problems parsing these
  