[Bug] No markLine drawn if one of the markLines is empty

[langkamp-aspen]

Version

6.1

Link to Minimal Reproduction

https://jsfiddle.net/Lvop3jc7/

Steps to Reproduce

1. Add a series with markLine and then inside the data of the markLine have one empty object
   markLine: { data: [ { "yAxis": 1 }, {}, { "yAxis": 3 }, ] }

Current Behavior

No markLine is rendered.
There is a error Uncaught TypeError: Cannot read properties of undefined (reading 'coord')

Expected Behavior

The empty markLine is skipped in rendering, but the other marklines are rendered. No error.

Environment

- OS: Windows 11
- Browser: Chrome
- Framework:

Any additional comments?

No response

[helgasoft]

workaround - for empty markLine.data use { yAxis:'-' } instead of { }

[aloktomarr]

Can I pick this issue?

Cause : - An empty {} entry in markLine.data is normalized by markLineTransform to [undefined, undefined, {...}].
markLineFilter then reads item[0]/coord/item[1].coord on those undefined endpoints, throwing

[TypeError: Cannot read properties of undefined (reading 'coord')], which aborts rendering of all markLines in the series.

Fix : [markLineFilter], now treats an item with a missing endpoint as invalid and filters it out (returns false), so the empty entry is skipped and the remaining valid markLines render normally. Added a unit test. PR incoming.