Merge pull request youngyangyang04#956 from Tickylime/master

Update 0707.设计链表.md

Author: youngyangyang04

problems/0707.设计链表.md

@@ -706,6 +706,9 @@ func (this *MyLinkedList) AddAtIndex(index int, val int) {
 		head = head.Next
 		index--
 	}
+	if index > 0 {
+		return
+	}
 	node := &Node{
 		Val: val,
 		//node.Next = MyLinkedList[index]