Null pointer dereference in `@safe` can be optimized away

[limepoutine]

Follow-up of #22113. The spec explicitly disallows optimizing away null pointer dereference. However, all DMD versions on run.dlang.io optimize away &(*null).

#22113 is implemented to not change previous behavior, but I think taking the address of *null should result in a segfault.

[xavierfingers]

Nice