Block exit button from terminating the installer while it's in progress. (#300)

* Block exit button from terminating the installer while it's in progress.

* Fix quit prompt not appearing when closing the game from the taskbar.

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Co-authored-by: Skyth <19259897+blueskythlikesclouds@users.noreply.github.com>

UnleashedRecomp/ui/game_window.cpp

@@ -24,7 +24,12 @@ int Window_OnSDLEvent(void*, SDL_Event* event)
         ImGui_ImplSDL2_ProcessEvent(event);
 
     for (auto listener : GetEventListeners())
-        listener->OnSDLEvent(event);
+    {
+        if (listener->OnSDLEvent(event))
+        {
+            return 0;
+        }
+    }
 
     switch (event->type)
     {