BuddyPress.org

Buddypress outputs a empty row somewhere and this causes an error in validation of the xml sitemap. My guess is there is a php closing tag followed by a newline in one php file.

Why do I think its buddypress?
I deactivated all plugins and reactivated them one by one. After activating buddypress the xml error occurred

This is the beginning of the sitemap (I hope the empty row at the beginning is visible)

<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet type="text/xsl" href="//-------/main-sitemap.xsl"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">

This is the error
XML Parsing Error: XML or text declaration not at start of entity