fix(tree): drag over leaf node causes error (#203)

CHANGELOG.en-US.md

@@ -1,5 +1,11 @@
 # CHANGELOG
 
+## Pending
+
+### Fixes
+
+- Fix `n-tree` drag over leaf node causes error, closes [#200](https://github.com/TuSimple/naive-ui/issues/200).
+
 ## 2.12.2 (2021-06-19)
 
 ### Fixes

CHANGELOG.zh-CN.md

@@ -1,5 +1,11 @@
 # CHANGELOG
 
+## Pending
+
+### Fixes
+
+- 修复 `n-tree` 拖拽悬浮叶节点报错，关闭 [#200](https://github.com/TuSimple/naive-ui/issues/200)
+
 ## 2.12.2 (2021-06-19)
 
 ### Fixes

src/tree/src/Tree.tsx

@@ -521,6 +521,8 @@ export default defineComponent({
         window.clearTimeout(expandTimerId)
         expandTimerId = null
       }
+      // Don't expand leaf node.
+      if (node.isLeaf) return
       nodeKeyToBeExpanded = node.key
       const expand = (): void => {
         if (nodeKeyToBeExpanded !== node.key) return