message: Fix updater not closing all main windows
  For some reason, using QCoreApplication::notify() with a QCloseEvent never reaches any MainWindow, so now they get closed explicitly
diff: #include "UpdateDialog.h"
  #include "UpToDateDialog.h"
  #include "conf/Settings.h"
  +#include "ui/MainWindow.h"
  #include <QApplication>
  #include <QCloseEvent>
  #include <QDialog>
  @@ -225,12 +226,20 @@ Updater::DownloadRef Updater::download(const QString &link) {
  void Updater::install(const DownloadRef &download) {
  // First try to close all windows. Disable quit on close.
  - QCloseEvent event;
  - QString errorText = tr("Unable to install update");
  bool quitOnClose = QGuiApplication::quitOnLastWindowClosed();
  QGuiApplication::setQuitOnLastWindowClosed(false);
  - bool rejected = (!qApp->notify(qApp, &event) || !event.isAccepted());
  +
  + bool rejected = false;
  + for (MainWindow *window : MainWindow::windows()) {
  + rejected = !window->close();
  + if (rejected) {
  + break;
  + }
  + }
  +
  QGuiApplication::setQuitOnLastWindowClosed(quitOnClose);
  +
  + QString errorText = tr("Unable to install update");
  if (rejected) {
  emit updateError(errorText,
  tr("Some windows failed to close. You can "
  