双y轴， value 为0时， getPosition取不到 y轴位置

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版本：3.8.10。
当数据记录里的 y轴数值 等于 0时，使用getPosition()，获取的position 为 { x: xxx , y: NaN }。
当数值不为0时，获取的position 就是正常的

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注意：不是用 https://antv-issue-helper.surge.sh 创建的 issue 会被立即关闭。

Start by reproducing the issue in F2 version 3.8.10 with a dual-y-axis chart containing a value of zero, then trace the getPosition() path. Done means getPosition() returns a finite y coordinate for zero-valued data as it does for nonzero values.

Written by the indexing model from the issue text.