[Susan Vose]

A few years answering this one, but still it might help someone.

Get the exact measurements of the image for example 900 x 900 pix
open a new window make the background colour whatever you need it to be, resize the background you need to 910 x 910 pix so it overlaps the artboard, paste your image on the top layer, hit export, in the export window click the image size tab, check “clip to artboard” and bingo no white lines even using matte colours.