This patch hides the rating widget when the rating is 0 stars to reduce visual clutter.
There are two cases with different behaviour:
- When a rating widget is read-only, only ratings with more than zero stars are visible
- When a rating widget isn't read-only, the same rule applies but it also becomes visible on hover or selection (works like the play/delete/enqueue buttons). This way users can still set ratings on tracks with no stars.