referencer-1.2.2 build error: no match for ‘operator==’

[Dominik Kriegner]

referencer fails to build on recent Linux systems (see Arch/Debian/Gentoo bugs at [1,2,3])

[1] https://aur.archlinux.org/packages/referencer/
[2] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=839353
[3] https://bugs.gentoo.org/show_bug.cgi?id=601174

The relevant error is:

Document.C: In member function ‘void Document::updateRelFileName(const Glib::ustring&)’:
Document.C:300:17: error: no match for ‘operator==’ (operand types are ‘Glib::RefPtr<Gio::File>’ and ‘int’)
    if (lib_path == 0) {
                 ^
Document.C:300:17: note: candidate: operator==(int, int) <built-in>
Document.C:300:17: note: no known conversion for argument 1 from ‘Glib::RefPtr<Gio::File>’ to ‘int’

Its fixed by the attached patch which was created by Askhat Bakarov at Arch Linux