Fixed a crash when attaching an image on the public chat

Attaching an image in chat on a public link (/s/<public-key>) or the embeddable web widget used to crash the whole page with a generic "this page couldn't load" error, right as the shopper tried to send their image.

The image thumbnail's tooltip was missing a piece of setup it needs on those two surfaces. It's fixed now: attaching an image works the same everywhere the assistant appears. No action needed on your side.