Layers without draw block shouldn't match

[sensescape]

trafficstars

When testing the bike interlay for Walkabout @nvkelso and I noticed that Tangram seems to be matching to layers without a draw block (that only contain nested sublayers that do include filters and draw blocks).

When no sublayer matches, then the parent layer (with no draw block) should be omitted from the list of matching styles.

In this case z-server-friend shouldn't be listed:

• Test location: http://localhost:8000/#16/52.6478/4.9723
• Code link: https://github.com/tangrams/walkabout-style/blob/sensescape/bike-interlay/walkabout-style.yaml#L4468-L4475

[bcamper]

This is currently working as intended: the list of layers is a debugging feature provided to show which layers the feature matches based on the layer filters. I'd like to provide additional info in the future about the draw blocks present on each layer. We may be able to adjust the behavior here but will need to look more.