Raster tip 🐛

[yurivish]

I noticed a small bug where a raster mark throws an error if you use the data-less raster({ fill: (x, y) => ... }) form and include a tip.

Notebook: https://observablehq.com/d/aff3900cd6feec56

I'm not sure if this is a simple or a complicated fix since it looks like index comes up a lot.

Edit: Unrelatedly, I noticed that the lineWidth option for the tip mark does not default to Inifinity. The documentation seems to state that it does (I think the text mark does, but the tip shows an ellipsis for long text by default).