add BT_SetTerminate to all threads

src/app_dialogs.cpp

@@ -674,6 +674,7 @@ void App::dialog_timelapse_export()
 void App::dialog_export_mp4()
 {
     std::thread([this] {
+        BT_SetTerminate();
         const int video_width = 1024;
         const int video_height = 512;
         const int video_frames = 500;