Clarified that the renderer should be destroyed before the window

I didn't add a note to SDL_DestroyWindow() because we actually protect against this case now, but it's useful information to know conceptually when working with the renderer.

include/SDL3/SDL_render.h

@@ -2007,10 +2007,9 @@ extern SDL_DECLSPEC int SDLCALL SDL_RenderPresent(SDL_Renderer *renderer);
 extern SDL_DECLSPEC void SDLCALL SDL_DestroyTexture(SDL_Texture *texture);
 
 /**
- * Destroy the rendering context for a window and free associated textures.
+ * Destroy the rendering context for a window and free all associated textures.
  *
- * If `renderer` is NULL, this function will return immediately after setting
- * the SDL error message to "Invalid renderer". See SDL_GetError().
+ * This should be called before destroying the associated window.
  *
  * \param renderer the rendering context.
  *

include/SDL3/SDL_video.h

@@ -2333,9 +2333,6 @@ extern SDL_DECLSPEC int SDLCALL SDL_FlashWindow(SDL_Window *window, SDL_FlashOpe
  * Any popups or modal windows owned by the window will be recursively
  * destroyed as well.
  *
- * If `window` is NULL, this function will return immediately after setting
- * the SDL error message to "Invalid window". See SDL_GetError().
- *
  * \param window the window to destroy.
  *
  * \since This function is available since SDL 3.0.0.