Line Chart with Point Markers seems not working

[ooasis]

Hi,

The "Line Chart with Point Markers" seems broken. The points are not shown.

I even tested with the demo chart with spec below.

<vega-lite :spec="demo_spec"></vega-lite>

where demon_spec is:

 {
  "$schema": "https://vega.github.io/schema/vega-lite/v2.6.0.json",
  "description": "Stock prices of 5 Tech Companies over Time.",
  "data": {"url": "https://vega.github.io/editor/data/stocks.csv"},
  "mark": {
    "type": "line",
    "point": true
  },
  "encoding": {
    "x": {"timeUnit": "year", "field": "date", "type": "temporal"},
    "y": {"aggregate":"mean", "field": "price", "type": "quantitative"},
    "color": {"field": "symbol", "type": "nominal"}
  }

-thanks