Change crosshair to only appear when hovering the layer's color box.

[ZachTRice]

In the layers sidebar, when a layer only has a single color (i.e. not a scale), a box with that color is shown. The row surrounding this area is display:block, with a crosshair on hover, meaning the crosshair appears even if you aren't hovering the color box. That wrapping row should be changed to either display:inline or the hover should be scoped to the child/children spans (will need to account for canvas scales too).