🥰 [FEATURE] do not show null data in Sankey

### 🥰 Features description [Please make everyone to understand it]

桑基图中，不显示节点数据为 null 的节点和边

### 🏞 What problem does this feature solve

### 🧐 What does the proposed API look like

ignoreNil: boolean

### 🚑 Any additional [like screenshots]

Start by locating the Sankey chart implementation and its option definitions; the issue names the proposed ignoreNil boolean but no files or tests. Confirm completion by verifying that enabling it omits null-valued nodes and edges while preserving other Sankey data.

Written by the indexing model from the issue text.