!2499 f2fs: fix to avoid NULL pointer dereference f2fs_write_end_io()

Merge Pull Request from: @ci-robot 
 
PR sync from: Zhihao Cheng <chengzhihao1@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/OLX4DRRGULHS4XLUVQ3DRLXONR2H5UM3/ 
 
https://gitee.com/src-openeuler/kernel/issues/I78FS1 
 
Link:https://gitee.com/openeuler/kernel/pulls/2499

 

Reviewed-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>