Bug report : an error msg occurs when adding a kblocks theme

When adding both yesterday and today a kblocks theme, I had an error message at the end. Still, the theme was added, and everything works. I suppose this is a bogus error message.

Hi, can you make a screenshot next time you see it?
What did it say?

It is too fast : a popup div appears saying “error” and it disappears after 2/3 seconds. But I’ll try to catch it if it happens again.