🐛 Remove zero length .gz in case of error
🐛 Remove zero length .gz in case of error

Otherwise the page won't load at all because the js/css/less files are
taken from the gz versions which are empty.

Introduced by #3497

TODO: Fix gzip encoding under Python 2 (gzip.compress doesn't exist)

foosel/OctoPrint,foosel/OctoPrint,foosel/OctoPrint,foosel/OctoPrint