From d4a01bfef0da5b80ca25f0962b02cefacc283476 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <icculus@icculus.org>
Date: Wed, 20 Apr 2022 14:07:30 -0400
Subject: [PATCH] os2: SDL_DestroyMutex should ignore NULL mutexes.

Every other backend does this, so this should match, now.
It's possible this was harmless, but we can avoid the system call
and the (likely?) debug message when it fails, though!
---
 src/thread/os2/SDL_sysmutex.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/thread/os2/SDL_sysmutex.c b/src/thread/os2/SDL_sysmutex.c
index 984ae10fe..d3fc7a3bd 100644
--- a/src/thread/os2/SDL_sysmutex.c
+++ b/src/thread/os2/SDL_sysmutex.c
@@ -56,12 +56,12 @@ SDL_CreateMutex(void)
 void
 SDL_DestroyMutex(SDL_mutex * mutex)
 {
-    ULONG ulRC;
     HMTX  hMtx = (HMTX)mutex;
-
-    ulRC = DosCloseMutexSem(hMtx);
-    if (ulRC != NO_ERROR) {
-        debug_os2("DosCloseMutexSem(), rc = %u", ulRC);
+    if (hMtx != NULLHANDLE) {
+        const ULONG ulRC = DosCloseMutexSem(hMtx);
+        if (ulRC != NO_ERROR) {
+            debug_os2("DosCloseMutexSem(), rc = %u", ulRC);
+        }
     }
 }