Chartist-js: ctPointLabels label undefined when 0

[srternasco]

I'm implementing ctPointLabels but I get undefined when serie value is 0.

What I'm doing wrong? Is this a bug?

new Chartist.Line(chart_wrapper, {
  labels: [1, 2, 3, 4, 5],
  series: [
    [1, 1, 8, 0, 7]
  ]
  },
  {
    axisX: {
      showGrid: false,
      showLabel: false,
      offset: 0
    },
    axisY: {
      showGrid: false,
      showLabel: false,
      offset: 0
    },
    chartPadding: {
      top: 15,
      right: 10,
      bottom: 0,
      left: 10
    },
    fullWidth: true,
    lineSmooth: false,
    showArea: true,
    plugins: [
      Chartist.plugins.ctPointLabels({
        labelOffset: {
          x: 0,
          y: -7
        },
        textAnchor: 'middle'
      })
    ]
  })

Thanks in advance.

[echosalik]

For anyone who has the same problem add the following line:
if(typeof d === "undefined") d = "0";
below this line:
function b(b, c) { var d = void 0 !== c.value.x && c.value.y ? c.value.x + ", " + c.value.y : c.value.y || c.value.x;