Fix crash when specific_node is -1

src/core/perfmodel/perfmodel.c

@@ -342,9 +342,11 @@ double starpu_task_expected_data_transfer_time(unsigned memory_node, struct star
 	{
 		starpu_data_handle_t handle = STARPU_TASK_GET_HANDLE(task, buffer);
 		enum starpu_data_access_mode mode = STARPU_TASK_GET_MODE(task, buffer);
-		unsigned node = memory_node;
+		unsigned node = -1;
 		if (task->cl->specific_nodes)
 			node = STARPU_CODELET_GET_NODE(task->cl, buffer);
+		if (node == -1)
+			node = memory_node;
 
 		penalty += starpu_data_expected_transfer_time(handle, node, mode);
 	}