!1958 block: don't get gendisk if queue has not been registered

Merge Pull Request from: @ci-robot 
 
PR sync from: Li Lingfeng <lilingfeng3@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/NZCTWHFD7VUC76P2MXXTMYM5IP5IEBSW/ 
 
https://gitee.com/openeuler/kernel/issues/I7XTQH 
 
Link:https://gitee.com/openeuler/kernel/pulls/1958

 

Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>