!4192 [sync] PR-4014: drm/dp_mst: Fix NULL deref in get_mst_branch_device_by_guid_helper()

Merge Pull Request from: @openeuler-sync-bot 
 

Origin pull request: 
https://gitee.com/openeuler/kernel/pulls/4014 
 
PR sync from: Baogen Shang <baogen.shang@outlook.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/B4J6O6LWC5A2ZIXQMSQ4NFTLTU2WNGQS/ 
 
https://gitee.com/openeuler/kernel/issues/I8AS5P 
 
Link:https://gitee.com/openeuler/kernel/pulls/4192

 

Reviewed-by: Jialin Zhang <zhangjialin11@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>