properly shut down and unref nm mainloop, fixes crash at shutdown

src/charon/plugins/nm/nm_plugin.c

@@ -63,8 +63,6 @@ static job_requeue_t run(private_nm_plugin_t *this)
 {
 	this->loop = g_main_loop_new(NULL, FALSE);
 	g_main_loop_run(this->loop);
-	g_main_loop_unref(this->loop);
-	
 	return JOB_REQUEUE_NONE;
 }
 
@@ -74,9 +72,13 @@ static job_requeue_t run(private_nm_plugin_t *this)
 static void destroy(private_nm_plugin_t *this)
 {
 	if (this->loop)
+	{
+		if (g_main_loop_is_running(this->loop))
 		{
 			g_main_loop_quit(this->loop);
 		}
+		g_main_loop_unref(this->loop);
+	}
 	if (this->plugin)
 	{
 		g_object_unref(this->plugin);