Expected Behavior

Tooltip should show actual dataset value.

Current Behavior

Tooltip for point on Y Axis with category scale and custom labels shows undefined instead of value.

Possible Solution

There is something wrong in category scale. We can provide not null object in config like yLabels: ['whatever'] to make it work but it looks like temporary fix.
file: scale.category.js
method: getLabelForIndex

if (data.yLabels && !isHorizontal) {
	return me.getRightValue(data.datasets[datasetIndex].data[index]);
}

Steps to Reproduce (for bugs)

https://codepen.io/anon/pen/jvraNR

Context

I'm trying to show category scale y axis in multi axis chart and have correct tooltip value.

Environment

• Chart.js version: 2.7.2
• Browser name and version: any