PHP Fatal error: singleton() Called without a class in when delete or click settings

[ghost]

Hi, this is a great module! I installed on SS 3.1. I can add panels, but when I click delete or settings I get this an internal server error and this in my server log:

PHP Fatal error: singleton() Called without a class in /home/sites/development/000_SILVERSTRIPE/www/framework/core/Core.php on line 366, referer: http://www.silverstripetest.hstc/admin/dashboard/

[unclecheese]

Something's really screwed up, because Core.php doesn't have a line 366. https://github.com/silverstripe/silverstripe-framework/blob/3.1/core/Core.php

[ghost]

Thanks for reply!
Well, my Core.php from 3.1 beta3, downloaded at July 7 has 514 lines, see the attachment.

[ghost]

Extra info: the error appears only in websites where I have the subsites module installed. Without the subsites module everything works fine. In a website where the subsites module was installed, the error disappeared after uninstalled in subsites module.