Fix mrview compilation through conflict resolution

- Remove code within cmd/mrview.cpp that originates from 6417a52 as part of #2689, which was erroneously added in 39240ad.
- Fix compilation of src/gui/mrview/file_open.cpp to coincide with changes in #2764; these were omitted from cherry-picks 39240ad and 0afe37b due to that file having already been removed during the course of #2689.

cmd/mrview.cpp

@@ -80,20 +80,6 @@ void usage() {
 }
 
 void run() {
-  GUI::App::setEventHandler([](QEvent *event) {
-    if (event->type() == QEvent::FileOpen) {
-      QFileOpenEvent *openEvent = static_cast<QFileOpenEvent *>(event);
-      std::vector<std::unique_ptr<MR::Header>> list;
-      try {
-        list.push_back(std::make_unique<MR::Header>(MR::Header::open(openEvent->file().toUtf8().data())));
-      } catch (Exception &E) {
-        E.display();
-      }
-      reinterpret_cast<MR::GUI::MRView::Window *>(MR::GUI::App::main_window)->add_images(list);
-    }
-    return false;
-  });
-  Q_INIT_RESOURCE(icons);
   GUI::MRView::Window window;
   MR::GUI::MRView::Sync::SyncManager sync; // sync allows syncing between mrview windows in different processes
   window.show();

src/gui/mrview/file_open.cpp

@@ -23,9 +23,9 @@ namespace GUI {
 bool App::event(QEvent *event) {
   if (event->type() == QEvent::FileOpen) {
     QFileOpenEvent *openEvent = static_cast<QFileOpenEvent *>(event);
-    vector<std::unique_ptr<MR::Header>> list;
+    std::vector<std::unique_ptr<MR::Header>> list;
     try {
-      list.push_back(make_unique<MR::Header>(MR::Header::open(openEvent->file().toUtf8().data())));
+      list.push_back(std::make_unique<MR::Header>(MR::Header::open(openEvent->file().toUtf8().data())));
     } catch (Exception &E) {
       E.display();
     }