!7586 powerpc/imc-pmu: Add a null pointer check in update_events_in_group()

Merge Pull Request from: @ci-robot 
 
PR sync from: Luo Gengkun <luogengkun2@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/MNNKCJ2KH5FANLAD2EDANWXTOGXBJKSB/ 
 
https://gitee.com/src-openeuler/kernel/issues/I9Q9J4 
 
Link:https://gitee.com/openeuler/kernel/pulls/7586

 

Reviewed-by: Liu YongQiang <liuyongqiang13@huawei.com>
Reviewed-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>