inquiry: fix edge case when answer is full size of reply buffer
inquiry: fix edge case when answer is full size of reply buffer

Right now if the user's answer is 1024 bytes exactly then we'll
call strlen() on an unterminated string.

This commit addresses the issue by avoiding the strlen() call and
instead using the already computed length.

https://bugzilla.gnome.org/show_bug.cgi?id=739593

Distrotech/gnome-online-accounts,ritzk/gnome-online-accounts,felipeborges/gnome-online-accounts,halfline/gnome-online-accounts,felipeborges/gnome-online-accounts,felipeborges/gnome-online-accounts,halfline/gnome-online-accounts,Distrotech/gnome-online-accounts,Distrotech/gnome-online-accounts,ritzk/gnome-online-accounts,ritzk/gnome-online-accounts,halfline/gnome-online-accounts