Error message

• Warning: Cannot modify header information - headers already sent by (output started at /home/slovcom/domains/gallery-afon.org/public_html/ua/includes/bootstrap.inc:1692) in drupal_send_headers() (line 1551 of /home/slovcom/domains/gallery-afon.org/public_html/ua/includes/bootstrap.inc).
• TypeError: Argument 1 passed to xmlsitemap_node_create_link() must be an instance of stdClass, bool given, called in /home/slovcom/domains/gallery-afon.org/public_html/ua/sites/all/modules/xmlsitemap/xmlsitemap_node/xmlsitemap_node.module on line 28 in xmlsitemap_node_create_link() (line 194 of /home/slovcom/domains/gallery-afon.org/public_html/ua/sites/all/modules/xmlsitemap/xmlsitemap_node/xmlsitemap_node.module).