object: Fix memory leak in resolve

The "name" string, allocated in gjs_get_string_id(), wasn't getting freed
at every exit point of the function. (It will be nice to clean this up in
1.49.x with our autoptr classes...)

After a certain point in the function it's not needed, so we just free
the string there.

https://bugzilla.gnome.org/show_bug.cgi?id=780171