我想写一个将两个升序链表合并（去重复值）的函数，但是写完了之后输出时只有表头和表尾会输出，求解为啥，这是我的函数
ElemSH* SlectSheng(ElemSH* h1,ElemSH* h2){
    ElemSH *hn,*t,*ins;
    hn=NULL;
    while(h1&&h2){
        if(h1->date<h2->date){
            ins=h1;
            h1=h1->next;
        }
        else{
            ins=h2;
            h2=h2->next;
        }
        if(!hn){
            hn=t=ins;
        }
        else{
            if(t->date==ins->date){
                t->next=ins->next;
                free(ins);
            }
            else{
                t->next=ins;
            }
        }
    }
    return hn;
}