Wrong root id for multidomain setup

[SventB]

If you have a multidomain setup and the root page for the domain the sitemap is requested is a shortcut, the root page for this domain is wrong, in function "fetchPagesFromTreeStructure" the determined root page then has id "0".

That has the result, that function "fetchPagesFromTreeStructure" returns all subpages of all(!!) domains configured in this backend.

The generated sitemap still includes only the pages for the current domain, but returning and processing all subpages results in invalid records in the realurl tables.