Treegraph chart throws error when setting legendSymbol to 'lineMarker'.

[jakubjanuchta]

Expected behaviour

When treegraph.legendSymbol is set to lineMarker, the chart doesn't break and there is no error in the console.

Actual behaviour

When treegraph.legendSymbol is set to lineMarker, the chart breaks and TypeError: Cannot read properties of undefined (reading 'indexOf') error is thrown.

Live demo with steps to reproduce

https://jsfiddle.net/BlackLabel/5avsd4hu/

Product version

Highcharts v11.1.0

Affected browser(s)

All