Allow calling OPENSSL_INIT_free() with NULL argument

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
(Merged from openssl#24681)

(cherry picked from commit d38f62e)

crypto/conf/conf_lib.c

@@ -410,6 +410,9 @@ int OPENSSL_INIT_set_config_appname(OPENSSL_INIT_SETTINGS *settings,
 
 void OPENSSL_INIT_free(OPENSSL_INIT_SETTINGS *settings)
 {
+    if (settings == NULL)
+        return;
+
     free(settings->filename);
     free(settings->appname);
     free(settings);