Fixed a crash if creating accelerated renderer after accessing window surface.

Partially fixes Bugzilla #3196.

src/video/SDL_video.c

@@ -1488,6 +1488,7 @@ SDL_RecreateWindow(SDL_Window * window, Uint32 flags)
     if (window->surface) {
         window->surface->flags &= ~SDL_DONTFREE;
         SDL_FreeSurface(window->surface);
+        window->surface = NULL;
     }
     if (_this->DestroyWindowFramebuffer) {
         _this->DestroyWindowFramebuffer(_this, window);