message: [qt] only allow https explorer links
  As reported by Fabian Braeunlein of PS Positive Security GmbH
diff: @@ -236,8 +236,9 @@ void TransactionView::setModel(WalletModel *_model)
  QStringList listUrls = _model->getOptionsModel()->getThirdPartyTxUrls().split("|", QString::SkipEmptyParts);
  for (int i = 0; i < listUrls.size(); ++i)
  {
  - QString host = QUrl(listUrls[i].trimmed(), QUrl::StrictMode).host();
  - if (!host.isEmpty())
  + QUrl url = QUrl(listUrls[i].trimmed(), QUrl::StrictMode);
  + QString host = url.host();
  + if (!host.isEmpty() && url.scheme() == "https")
  {
  QAction *thirdPartyTxUrlAction = new QAction(host, this); // use host as menu item label
  if (i == 0)
  