message: fix x axis label
diff: @@ -360,7 +360,7 @@ function nvd3Vis(slice, payload) {
  if (fd.x_axis_label && fd.x_axis_label !== '' && chart.xAxis) {
  let distance = 0;
  - if (fd.bottom_margin) {
  + if (fd.bottom_margin && !isNaN(fd.bottom_margin)) {
  distance = fd.bottom_margin - 50;
  }
  chart.xAxis.axisLabel(fd.x_axis_label).axisLabelDistance(distance);
  