libopenarc: arc_free() semantics should match free()

Author: flowerysong

CHANGELOG.md

@@ -11,6 +11,7 @@ All notable changes to this project will be documented in this file.
 ### Removed
 
 ### Fixed
+- libopenarc - `arc_free()` accepts NULL.
 
 ## [1.1.0](https://github.com/flowerysong/OpenARC/releases/tag/v1.1.0) - 2024-11-05
 

libopenarc/arc.c

@@ -2397,6 +2397,11 @@ arc_free(ARC_MESSAGE *msg)
     struct arc_hdrfield *h;
     struct arc_hdrfield *tmp;
 
+    if (msg == NULL)
+    {
+        return;
+    }
+
     if (msg->arc_error != NULL)
     {
         ARC_FREE(msg->arc_error);