SDL: audio: Make sure `device->hidden` is NULL after CloseDevice

SDL Commits
1

https://github.com/libsdl-org/SDL/commit/121a2dce1562a94eb18c90d92a433f51f8ebac82

From 121a2dce1562a94eb18c90d92a433f51f8ebac82 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Wed, 5 Jul 2023 02:44:52 -0400
Subject: [PATCH] audio: Make sure `device->hidden` is NULL after CloseDevice

---
 src/audio/SDL_audio.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/audio/SDL_audio.c b/src/audio/SDL_audio.c
index 5ce08c268453..6ddaafe76bfc 100644
--- a/src/audio/SDL_audio.c
+++ b/src/audio/SDL_audio.c
@@ -1091,6 +1091,7 @@ static void ClosePhysicalAudioDevice(SDL_AudioDevice *device)
     if (device->is_opened) {
         current_audio.impl.CloseDevice(device);  // if ProvidesOwnCallbackThread, this must join on any existing device thread before returning!
         device->is_opened = SDL_FALSE;
+        device->hidden = NULL;  // just in case.
     }
 
     if (device->work_buffer) {