WebExtension breaks in FireFox 42

Hi guys, I’m developing FF-addon using latest WebExtension techniques. I got it almost done and it worked good enough in FireFox Nightlies, but after couple of tries to start it in FF Stable 42, I found that I was getting the next error on widget start:
ReferenceError: state is not defined, in resource://gre/modules/ExtensionContent.jsm 331:42.

As I can see from sources of the specified file - the error appears in DocumentManager’s executeScript - method, on the following lines:
// TODO: Somehow make sure we have the right permissions for this origin!
// FIXME: Need to keep this around so that I will execute it later if we’re not in the right state.
context.execute(script, scheduled => scheduled == state);

Does anybody know what is the root cause for this issue and if it’s located somewhere in my code or not?

I would appreciate any suggestions or guesses, thank you in advance.

WebExtensions are still under development, so some APIs that work on Nightly won’t work in release. The planned initial release for the API is early next year, and in the meantime you can’t expect all APIs to work well. You can track progress at http://arewewebextensionsyet.com/