Call to a member function getConfiguration() on a non-object

OK, so let me walk through this for second, I take you are doing this:

1) enable AT Core
2) generate sub-theme
3) enable new sub-theme

When or where does the error occur, is it right after you enable the sub-theme, aka as the Appearance page reloads after clicking enable, or when you visit another page?

What version of Drupal 8 are you running, is it an alpha or dev/head?

Is your site in English or another language/multilingual?

Hmmm, on the latest Drupal 8 head I can reproduce this, but only if the cache is not cleared before trying to enable the new sub-theme, I need to look at this more.

Adding references, as per https://api.drupal.org/api/drupal/core%21modules%21language%21lib%21Drup...

The error is initially caused by some config files for AT Blocks module that I left in the sub theme /config/ directory, I can remove those for now, I am not entirely sure how to include custom configuration for 3rd party modules (non core modules), this is not clear to me at the moment, I need to ask someone in Drupal core dev and CMI how this is supposed to work (could be incomplete in D8 at the moment etc).

I'll remove these files and call this fixed for now, so the issue will go away. Basically if Drupal 8 ships with everything as a blocks (Page title, site branding (logo, site name etc) this is moot issue as those config files will be removed forever and the AT Blocks module will be retired, that is what I am hoping for :) but if not, then I would like to ship some config for those blocks in the sub-theme if that makes sense, right now this is not important and we can remove the config files.

Note that AT Blocks modules does not have to be installed to get this issue, whats happening is the config files are being parsed and somewhere in there is a the problem, I am not entirely sure what.