fix(tree-select): After deleting the last child node of the parent node, another child node is selected. #3508 #3586 (#4047)

Author: jeryqwq

components/vc-tree-select/src/Select.jsx

@@ -874,12 +874,24 @@ const Select = defineComponent({
     },
 
     onSearchInputKeyDown(event) {
-      const { _searchValue: searchValue, _valueList: valueList } = this.$data;
+      const { _searchValue: searchValue, _valueList: valueList, _valueEntities: valueEntities } = this.$data;
 
       const { keyCode } = event;
 
       if (KeyCode.BACKSPACE === keyCode && this.isMultiple() && !searchValue && valueList.length) {
-        const lastValue = valueList[valueList.length - 1].value;
+        let lastValue = valueList[valueList.length - 1].value;
+        const { treeCheckStrictly } = this.$props;
+        if(!treeCheckStrictly) {
+          let cur = valueEntities[lastValue];
+          while(cur) {
+            if(valueList.some(j => j.value === cur.value)) {
+              lastValue = cur.value;
+              cur = cur.parent;
+            }else{
+              cur = null
+            }
+          }
+        }
         this.onMultipleSelectorRemove(event, lastValue);
       }
     },