SDL: audio: Fixed copy/paste error that was checking wrong variable.

From ff57867516d4f8044283ec4a8554c27782e525a6 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 3 Oct 2023 14:58:05 -0400
Subject: [PATCH] audio: Fixed copy/paste error that was checking wrong
 variable.

Fixes #8342.
---
 src/audio/SDL_audio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/audio/SDL_audio.c b/src/audio/SDL_audio.c
index b9a73247bc4c..cb2736982cc6 100644
--- a/src/audio/SDL_audio.c
+++ b/src/audio/SDL_audio.c
@@ -1565,7 +1565,7 @@ int SDL_SetAudioPostmixCallback(SDL_AudioDeviceID devid, SDL_AudioPostmixCallbac
         SDL_AudioDevice *device = logdev->physical_device;
         if (callback && !device->postmix_buffer) {
             device->postmix_buffer = (float *)SDL_aligned_alloc(SDL_SIMDGetAlignment(), device->work_buffer_size);
-            if (device->mix_buffer == NULL) {
+            if (device->postmix_buffer == NULL) {
                 retval = SDL_OutOfMemory();
             }
         }