Firefox: images loaded via <img srcset="..."> are shown in 'other' column

[xofe]

Commit ad4b9b7 changed type 21's mapping from image to imageset, and it seems this causes images on sites using <img srcset="..."> to be categorised in the other column, rather than the image column.

Example: http://www.ghacks.net/2017/04/02/desktop-environments-lxde/ (you may need to resize browser window to trigger their load, as they have a max-width: 1024px media condition)

Browser: Firefox 53b8; uMatrix version: 0.9.9b11