!1849 fs: jfs: fix possible NULL pointer dereference in dbFree()

Merge Pull Request from: @ci-robot 
 
PR sync from: Li Nan <linan122@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/YC56BN75ZGPSQ5YHGT6A54EO2N7GUO7G/ 
 
https://gitee.com/src-openeuler/kernel/issues/I7TT9F 
 
Link:https://gitee.com/openeuler/kernel/pulls/1849

 

Reviewed-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Liu YongQiang <liuyongqiang13@huawei.com>