Patch provided by German Rumm <german.rumm@gmail.com> to avoid a fatal error in assertLink (when the link with a label does not exists in a page)
Patch provided by German Rumm <german.rumm@gmail.com> to avoid a fatal error in assertLink
(when the link with a label does not exists in a page)

GerHobbelt/simpletest,GerHobbelt/simpletest,GerHobbelt/simpletest