fix(MarkLineView): skip invalid markLine items that were normalized to undefined

[waterWang]

Fix: skip invalid markLine items that were normalized to undefined

Issue

Fixes #21683

Problem

When a markLine data entry is an empty object {}:

markLine: {
    data: [
        { yAxis: 1 },
        {},          // <-- empty entry
        { yAxis: 3 }
    ]
}

markLineTransform normalizes the empty object to [undefined, undefined, {...}].
The subsequent markLineFilter call then crashes on item[0].coord because item[0] is undefined,
causing no markLines to be rendered at all — not even the valid ones.

Root Cause

In markLineTransform, the else branch (invalid data) sets itemArray = [], but the function continues to construct normalizedItem from itemArray[0], itemArray[1], itemArray[2] — all of which are undefined. The filter then crashes on the undefined values.

Fix

Added a guard in markLineFilter to return false (skip) when item[0] or item[1] is undefined, which is the expected behavior: invalid entries should be silently skipped and valid entries should still render.

Verification

• Valid markLines continue to render when no empty entries exist
• An empty {} entry is silently skipped without error
• Other valid markLines in the same data array still render normally

[echarts-bot]

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