Can not slice a GeoJSON file containing just points

Prompted by https://stackoverflow.com/questions/44707862/how-to-add-geojson-points-as-a-vector-tile-in-leaflet

I tried to load a GeoJSON file containing only points (the one referenced in the SO question) like so:

    fetch('https://raw.githubusercontent.com/evantdailey/map_testing/master/site1.geo.json').then(function(response){
      return response.json();
    }).then(function(json){
      var points = L.geoJson(json);
      map.fitBounds(points.getBounds());

      var vectorGrid = L.vectorGrid.slicer( json, {
        maxZoom: 20,
        rendererFactory: L.svg.tile,
        vectorTileLayerStyles: {
          sliced: {
            weight: 2,
            color: 'red',
            opacity: 1,
            fillColor: 'yellow',
            fill: true,
            radius: 6,
            fillOpacity: 0.7
          }
        }
      });
      
      vectorGrid.addTo(map);
    })

Playground here. The GeoJSON is valid as per geojsonlint, and it loads if the code is changed to read var points = L.geoJson(json).addTo(map);

After a few minutes looking at the problem, I've discovered at least two problems when slicing geojson points:

• The L.VectorGrid.Slicer does not have a minZoom nor maxZoom. This affects the behaviour of L.GridLayer.update(), as this._tileZoom becomes undefined. The end result is that no tiles are displayed, so no tiles are requested to geojson-vt. Setting a default minZoom and maxZoom should alleviate this. I do not know if the default maxZoom of 14 is being overwritten, or if there is some other race condition elsewhere.

• If this._tileZoom is hacked during debug to allow some tiles to be requested, then _mkFeatureParts throws an exception. It is reminiscent of the cases where a point geometry is used but a linestring geometry is expected.

Unfortunately I don't have the time to debug this problem thoroughly.

Reproduce the issue with the linked point-only GeoJSON and the Leaflet.VectorGrid.Slicer example. Start by tracing L.GridLayer.update(), L.VectorGrid.Slicer, and the geojson-vt call, then inspect _mkFeatureParts for the point geometry failure. Done means point-only GeoJSON is sliced and rendered without missing tiles or exceptions.