Get redirect loop when there is no $options['purl'] on purl_goto

Hello,
i'm working with OpenScholar distribution and i have several sites. My node that relate to a site have the 10 nid. When accessing to node/10 i'm getting a redirect loop because in the first time there is no $options['purl'] arguments in the purl_goto function. The address did changed to the path of the node(book/foobar) but there is a loop redirect.

I made patch that check for the existent of the $options['purl'].