[Bug c++/115664] -Wnonnull-compare breaks templated methods

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115664

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Basically `dynamic_cast<T*>(this)` becomes just this if `T == Object` here and
then we warn because this is compared with nullptr.