This tests checks that isLinked can now be used safely as it eventually plays
well with transaction machinery.

  >>> self.setRoles(('Manager',))

Add bad link, should not raise exception and there should not be any
references added.

  >>> self.setText(portal.doc1, '<a href="ö?foo=bar&baz=bam">bug</a>')
  >>> portal.doc1.getReferences()
  []