a minimal example to reproduce the Cannot read property '0' of null in clipCells()
error message described in d3-voronoi github issue 16
the code for the d3-voronoi-scatterplot
chart plugin is at https://github.com/micahstubbs/d3-voronoi-scatterplot
https://d3js.org/d3.v4.min.js
https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.js