[Bug libstdc++/65257] cin not working with empty string when _GLIBCXX_DEBUG is defined on Windows

[nightstrike at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65257

--- Comment #2 from nightstrike <nightstrike at gmail dot com> ---
I should clarify that I tested this with mingw-w64, not mingw.org where the bug
was originally reported.