gk20a_gr_get_channel_from_ctx() could return NULL as a result fault_ch could be null JIRA GPUT19X-7 Change-Id: If89507d3d3fa5a95ba75c4a90eb212d0c8b2214a Signed-off-by: Seema Khowala <seemaj@nvidia.com> Reviewed-on: http://git-master/r/1323255 Reviewed-by: Automatic_Commit_Validation_User Reviewed-by: svccoveritychecker <svccoveritychecker@nvidia.com> GVS: Gerrit_Virtual_Submit Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>