The log website responds with a blank message when a sticker is sent

[Catdontpat]

The modmail logviewer displays a blank message whenever a sticker is sent, It would be best to have it display an image like in the embed

[raidensakura]

This also require a change in Modmail since it does not save sticker payload into the db.

Linked issue: https://github.com/modmail-dev/Modmail/issues/3240