add code in render_related_url to handle link with missing url
improve handling of undef url in render_related_url
fix missing variable
Merge branch 'master' of https://github.com/eprints/eprints into 20140725-undef-in-render_related_url

Conflicts:
	perl_lib/EPrints/Extras.pm
Merge pull request #250 from QUTlib/20140725-undef-in-render_related_url

add code in render_related_url to handle link with missing 'url'