[Bug sanitizer/79572] [6/7 Regression] reference binding to null pointer not reported with -fsanitize=undefined

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79572

--- Comment #12 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 41029
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41029&action=edit
gcc7-pr79572.patch

Untested fix.