avoid double SDL_Quit() (#625)

`SDL_Quit` is already called by the smart pointer de-constructor

Co-authored-by: Turánszki János <turanszkij@users.noreply.github.com>

Editor/main_SDL2.cpp

@@ -160,6 +160,5 @@ int main(int argc, char *argv[])
 
     int ret = sdl_loop(editor);
 
-    SDL_Quit();
     return ret;
 }