Hi,
This was indeed a false positive. I have disabled the detection on this file. Please make sure your Avast is updated and streaming updates are enabled (are by default), disable and enable shields (just to be sure) and see if it you are getting any more popups.
If the detection appears and is different from the last one (a.gfx.ms/App0x_ia82xQ2gj6yACclap57JwQ2.js), please do post a printscreen.
Thanks for the report!