wiiu/render: SDL_GetWindowSurface is needed to create the framebuffer

src/render/wiiu/SDL_render_wiiu.c

@@ -41,9 +41,15 @@ SDL_RenderDriver WIIU_RenderDriver;
 
 SDL_Renderer *WIIU_SDL_CreateRenderer(SDL_Window * window, Uint32 flags)
 {
+    SDL_Surface *surface;
     SDL_Renderer *renderer;
     WIIU_RenderData *data;
 
+    surface = SDL_GetWindowSurface(window);
+    if (!surface) {
+        return NULL;
+    }
+
     renderer = (SDL_Renderer *) SDL_calloc(1, sizeof(*renderer));
     if (!renderer) {
         SDL_OutOfMemory();