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

These records connect through source-stated identifiers. Shared identifiers or dates alone do not establish shared exposure, root cause or applicability.

CVE-2023-52675 · Microsoft / collected KEV context

cve-program · CVE-2023-52675

• https://git.kernel.org/stable/c/75fc599bcdcb1de093c9ced2e3cccc832f3787f3
• https://git.kernel.org/stable/c/1e80aa25d186a7aa212df5acd8c75f55ac8dae34
• https://git.kernel.org/stable/c/5a669f3511d273c8c1ab1c1d268fbcdf53fc7a05
• https://git.kernel.org/stable/c/f105c263009839d80fad6998324a4e1b3511cba0
• https://git.kernel.org/stable/c/a2da3f9b1a1019c887ee1d164475a8fcdb0a3fec
• https://git.kernel.org/stable/c/024352f7928b28f53609660663329d8c0f4ad032
• https://git.kernel.org/stable/c/c7d828e12b326ea50fb80c369d7aa87519ed14c6
• https://git.kernel.org/stable/c/0a233867a39078ebb0f575e2948593bbff5826b3

No related operational record is retained in the current change model.