Fatal Error unknown

Sun, 02 Jun 2013 12:38:15 +0000
Message: PHP notice in file /wcf/lib/system/style/lessc.inc.php (2056): Undefined property: stdClass::$parent
File: /wcf/lib/system/WCF.class.php (286)
PHP version: 5.3.24
WCF version: 2.0.0 Beta 2 (Maelstrom)
Request URI: /index.php/BoardList/
User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:21.0) Gecko/20100101 Firefox/21.0
Stacktrace: 
  #0 /wcf/lib/system/style/lessc.inc.php(2056): wcf\system\WCF::handleError(8, 'Undefined prope...', '/home/milleni2/...', 2056, Array)
  #1 /wcf/lib/system/style/lessc.inc.php(1575): lessc_parser->parse('@import "style/...')
  #2 /wcf/lib/system/style/StyleCompiler.class.php(178): lessc->compile('@import "style/...')
  #3 /wcf/lib/system/style/StyleCompiler.class.php(76): wcf\system\style\StyleCompiler->compileStylesheet('/home/milleni2/...', Array, Array, '/* ### blue tem...', Object(wcf\system\Callback))
  #4 /wcf/lib/system/style/StyleHandler.class.php(133): wcf\system\style\StyleCompiler->compile(Object(wcf\data\style\Style))
  #5 /wcf/templates/compiled/0_wbb_1_headInclude.php(79): wcf\system\style\StyleHandler->getStylesheet()
  #6 /wcf/lib/system/template/TemplateEngine.class.php(324): include('/home/milleni2/...')
  #7 /wcf/lib/system/template/TemplateEngine.class.php(689): wcf\system\template\TemplateEngine->display('headInclude', 'wbb', false)
  #8 /wcf/templates/compiled/0_wbb_1_boardList.php(33): wcf\system\template\TemplateEngine->includeTemplate('headInclude', 'wbb', Array, 0)
  #9 /wcf/lib/system/template/TemplateEngine.class.php(324): include('/home/milleni2/...')
  #10 /wcf/lib/page/AbstractPage.class.php(205): wcf\system\template\TemplateEngine->display('boardList', 'wbb')
  #11 /wcf/lib/page/AbstractPage.class.php(86): wcf\page\AbstractPage->show()
  #12 /wcf/lib/system/request/Request.class.php(58): wcf\page\AbstractPage->__run()
  #13 /wcf/lib/system/request/RequestHandler.class.php(93): wcf\system\request\Request->execute()
  #14 /index.php(10): wcf\system\request\RequestHandler->handle('wbb')
  #15 {main}