sdl12-compat: SDL_OpenAudio: SDL_assert(audio_cbdata == NULL) before assigning to it

SDL Commits
1 
From 808f1e7e580ea651d639c5e79638cfe46b1c41a4 Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Thu, 4 Mar 2021 13:51:56 +0300
Subject: [PATCH] SDL_OpenAudio: SDL_assert(audio_cbdata == NULL) before
 assigning to it

---
 src/SDL12_compat.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/SDL12_compat.c b/src/SDL12_compat.c
index 997d9a3..76fd931 100644
--- a/src/SDL12_compat.c
+++ b/src/SDL12_compat.c
@@ -4514,6 +4514,7 @@ SDL_OpenAudio(SDL_AudioSpec *want, SDL_AudioSpec *obtained)
         SDL20_free(data);
     } else {
         data->silence = want->silence;
+        SDL_assert(audio_cbdata==NULL);
         audio_cbdata = data;
         if (obtained) {
             SDL_memcpy(obtained, want, sizeof (SDL_AudioSpec));