Avoid _get_func() consuming reference from input info

Fix of leak in 4c9424e1 was a bit
overaggressive, stealing also one reference from input 'info'
argument.

Also fixes another bug in that commit - local 'func' shadowing the
return value, causing that function always returned NULL even when
some result was actually found.

https://bugzilla.gnome.org/show_bug.cgi?id=673282