[Feat]: 柱状图hover到空白区域怎么不显示tooltip

### Describe the feature / 功能描述

如上图，堆叠柱状图hover到空白区域会出现tooltip，更希望的是hover到实体柱上再出现tooltip。

### Are you willing to contribute? / 是否愿意参与贡献？

Please select / 请选择

No source file or test is named. Start by reproducing the stacked bar chart hover behavior shown in the issue, then locate the chart's hover and tooltip entry points. Done means hovering blank space shows no tooltip while hovering an actual bar still displays the tooltip.

Written by the indexing model from the issue text.