LU-14307 quota: fix NULL pointer dereference

LU-14307 quota: fix NULL pointer dereference

Fix NULL pointer dereference at 0x20 in
qmt_trans_start_with_slv->lquota_lqe_debug.

HPE-bug-id: LUS-9662
Change-Id: Iead0df053ae0dcb7453c1910a4b4b7a3728da829
Signed-off-by: Sergey Cheremencev <sergey.cheremencev@hpe.com>
Reviewed-on: https://review.whamcloud.com/41264
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>