Some top grid lines are missing when min value of y axis is set

[piotrp]

Description

Using axis․y․min may result in missing grid lines:

I would expect each tick on y axis to have its own line, but depending source values some lines may be missing.

Steps to check or reproduce

JSFiddle: https://jsfiddle.net/vc0hux95/

bb.generate({
  data: {
    columns: [
	    ["data1", 130, 340, 200, 500, 250, 350]
    ],
    type: "line"
  },
  axis: {
    y: {
      min: 0
    }
  },
  grid: {
    y: {
      show: true
    }
  },
  bindto: "#lineChart"
});

[netil]

This could be a side effect from the changes of #2715.
I'll look into. @piotrp thanks for the report.

[netil]

@piotrp
After digging, found that the issue happens because of grid.y.ticks option default value.
The option has 10 as default value, which limiting display 10 grid lines.

For workaround, give some value greater than the y axis tick count as grid.y.ticks=20.

Defaulting to grid ticks count to 10, seems counter intuitive.
Because, when grid.y.show=true is set, user will expect to be shown full grid lines.

Removing default value looks more reasonable in this case.