Seems that it is a problem form the GitHub side. We are not getting the proper response and that is why Exception is thrown.

ok hmm why i wonder is value was: nil. instead of value was: null or what ever But if it is a github response issue we can't fix this our self.

Just had the same issue creating an issue here

This comment was created with the J!Tracker Application at issues.joomla.org/jtracker/570.

Someone try submitting an issue from the app please? With any luck, I've added a logger statement that should give us some more data to work with.

just did. same error message on screen - hope you got something in the logs

This comment was created with the J!Tracker Application at issues.joomla.org/jtracker/570.

Should be fixed - joomla/joomla-cms#5265 - That was created from my local install

Issue was fixed by this change - 0168b6d

Just successfully created a new issue - thanks

This comment was created with the J!Tracker Application at issues.joomla.org/jtracker/570.

@mbabker thank you :) I wouldn't ever think that it is a problem in our code, because it was working and then just stopped

It looks like GitHub started enforcing strict typehinting on API endpoints. The Joomla Framework code that method is derived from had the same default declaration, which has worked fine for ~3 years. It is what it is.