[Bug rtl-optimization/64815] ICE caused by volatile_refs_p doesn't skip NULL operand

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64815

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I don't think you need to call volatile_refs_p on the notes part of the
instruciton.