SDL: SDL_sysmutex.c: fix void return compile error

From dd4636e3fde23da30eb393af841949b09bd3a86e Mon Sep 17 00:00:00 2001
From: Mark Delk <[EMAIL REDACTED]>
Date: Thu, 21 Mar 2024 13:11:49 -0500
Subject: [PATCH] SDL_sysmutex.c: fix void return compile error

---
 src/thread/pthread/SDL_sysmutex.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/thread/pthread/SDL_sysmutex.c b/src/thread/pthread/SDL_sysmutex.c
index 07d35cfb970fa..79dba13312a9e 100644
--- a/src/thread/pthread/SDL_sysmutex.c
+++ b/src/thread/pthread/SDL_sysmutex.c
@@ -141,7 +141,8 @@ void SDL_UnlockMutex(SDL_Mutex *mutex) SDL_NO_THREAD_SAFETY_ANALYSIS // clang do
                 pthread_mutex_unlock(&mutex->id);
             }
         } else {
-            return SDL_SetError("mutex not owned by this thread");
+            SDL_SetError("mutex not owned by this thread");
+            return;
         }
 
 #else