funopen: Fix memory leak in funopen_close() when closefn is NULL

We need to free the cookiewrap even when the closefn method is NULL.

Warned-by: gcc ASAN

src/funopen.c

@@ -87,10 +87,10 @@ funopen_close(void *cookie)
 	struct funopen_cookie *cookiewrap = cookie;
 	int rc;
 
-	if (cookiewrap->closefn == NULL)
-		return 0;
-
-	rc = cookiewrap->closefn(cookiewrap->orig_cookie);
+	if (cookiewrap->closefn)
+		rc = cookiewrap->closefn(cookiewrap->orig_cookie);
+	else
+		rc = 0;
 
 	free(cookiewrap);