下面函数用“哑结点”统一处理删除单向链表中的头结点与中间结点。横线处应填（ ）。

1struct Node{                                                          2   int val;                                                           3   Node* next;                                                        4   Node(int v):val(v),next(nullptr){}                                 5};                                                                    6                                                                      7Node* eraseAll(Node* head, int x){                                    8   Node dummy(0);                                                     9   dummy.next = head;                                                 10   Node* cur = &dummy;                                                11   while(cur->next){                                                  12      if(cur->next->val == x){                                        13        Node* del = cur->next;                                        14        ______________________                                        15        delete del;                                                   16      }else cur = cur->next;                                          17   }                                                                  18   return dummy.next;                                                 19}