Misplaced images should consider paths that *would* be expected, if cover artists were specified

[towerofnix]

Similar to #304: if an image is shown as misplaced, it should be indicated if the reason it's misplaced is because the directly corresponding album or track does not have a Cover Artists field. (Not even an update value—it's simply unspecified in the YAML.)

Lack of clarity caught Jebb: #software-support and is something we've run into too. It's not plainly obvious that Cover Artists is required to make a track/album be considered to have art at at all!