Labels are not present if text size is 0 at source max zoom

[mourner]

If text size is evaluated as 0 on a source max zoom (e.g. z15), labels won't appear even if the size gets non-zero on higher zooms.

For GeoJSON sources, the workaround is just bumping source maxzoom, and we're going to make it higher by default, but this is still a bug.

cc @lucaswoj @samanpwbb

[victorbello]

I've seen this happen.

[lucaswoj]

This might be related to #1792 or https://github.com/mapbox/mapbox-gl-js/blob/master/js/data/bucket.js#L175-L188

[ansis]

fixed by d3ffe37

tested with https://gist.github.com/ansis/41e54263ca5eef929443