g-i: Fix use after free in scanner
g-i: Fix use after free in scanner

Fixes https://gitlab.gnome.org/GNOME/vala/issues/674

frida/vala,GNOME/vala,GNOME/vala,frida/vala,frida/vala,frida/vala,GNOME/vala,GNOME/vala,frida/vala