fix bencmark crash on ResyberryPi3 Issuse#441 (#442)

src/serializer/tm/tm2_serializer.c

@@ -870,10 +870,7 @@ static int unload_graph(struct serializer* s, struct ir_graph* graph, void* s_pr
     struct tm2_priv* priv = ( struct tm2_priv* )s_priv;
 
     if (priv->base)
-    {
         sys_free(( void* )priv->base);
-        priv->base = NULL;
-    }
 
     graph->serializer = NULL;
     graph->serializer_priv = NULL;