schedule: fix panic during hot schedule (#3483)
schedule: fix panic during hot schedule (#3483)

* fix target

Signed-off-by: Song Gao <f222f204032533a6fcbe6e5ff6aed541ec6b4541@163.com>

* address the comment

Signed-off-by: Song Gao <f222f204032533a6fcbe6e5ff6aed541ec6b4541@163.com>
pingcap/pd,pingcap/pd