[Bug libstdc++/86130] Expect SIGSEGV but program just silently exits

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86130

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I don't know the original reason for handling null pointers here, but it's
consistent with glibc's printf which prints "(null)" when a null pointer is
provided for a %s specifier.

Removing this longstanding behaviour now could break an unnknown number of
programs which are (impicitly or explicitly) relying on this behaviour of
libstdc++.

It's not at all clear to me that crashing is preferable.