Release build searches for empty file name /.js

Made a fresh workspace with the latest sencha cmd 5.0.2.270. Generated an app into in.

The development loads well, but the production build tries to load file with no name and gets a 404

GET http://ift.tt/1CRCBUX 404 (Not Found)

I can't understand what it is searching for. Development is not complaining at all.

I made an archive with it http://ift.tt/1CRCBV1 (~600kb)

Please advise. Spent three days already. I'm really very new to ext js but not to development.

Any input is welcome.

Thank you.

Release build searches for empty file name /.js