좀긴데 좀봐줘요 형들 ㅠㅠ 한줄때문에 미치겠음

검색은 제대로 되는데

입력한 해당 data가 없으면 에러문구를 출력해주는 부분

   if(target ==NULL)
   {
    cout <<"Spotted Data is not in ... " <<endl;
    return false;
   }
이부분이 안되........... if(        ) 이부분에 target ==NULL 이 잘못된건가 ?? ㅠㅠ

분할파일이 4개라 너무 복잡할듯싶어서 헤더파일 두개는 안올릴게......

이게메인이구...........

-----------------------------------------
#include "Tree.h"

void main()
{
 cout <<"Binary Tree Test" <<endl;

 Tree BT;

 BT.Insert_Node(50);
 BT.Insert_Node(25);
 BT.Insert_Node(75);
 BT.Insert_Node(100);
 BT.Insert_Node(30);
 BT.Insert_Node(10);

 BT.Display();

 int i;
 cout <<"데이터 검색 : ";
 cin >>i;

 BT.Search_Node(i);
}
------------------------------------------

이게 cpp파일이야 ㅠㅠ
===================================================
#include "Tree.h"

bool Tree ::Insert_Node(int value)
{
 Node* newNode;
 newNode =new Node(value);

 if(_Size ==NULL)
 {
  _Root =newNode;
 }

 else
 {
  Node* runner =_Root;

  while(runner !=NULL)
  {
   if(newNode ->GetData() <runner ->GetData())
   {
    if(runner -> Get_LChild() ==NULL)
    {
     runner ->Set_LChild(newNode);
     break;
    }
    else
     runner =runner -> Get_LChild();
   }

   else if(newNode ->GetData() >runner ->GetData())
   {
    if(runner -> Get_RChild() ==NULL)
    {
     runner ->SetRChild(newNode);
     break;
    }
    else
     runner =runner -> Get_RChild();
   }

   else
   {
    cout <<"Data already exists in Tree! " <<endl;
    return false;
   }
  }
 }
 _Size++;
 return true;
}

bool Tree ::Search_Node(int target)
{
 Node* runner =_Root;

 if(_Root ==NULL)
 {
  cout <<"Tree is Empty! So I can\'t find Data" <<endl;
  return false;
 }

 else
 {
  while(target != runner -> GetData())
  {
   cout <<runner -> GetData() <<" ";
   if(target <runner ->GetData())
    runner =runner -> Get_LChild();
   else if(target >runner ->GetData())
    runner =runner ->Get_RChild();

   if(target ==NULL)
   {
    cout <<"Spotted Data is not in ... " <<endl;
    return false;
   }
  }
  cout <<runner -> GetData() <<endl;
  return true;
 }
}

void Tree ::Display()
{
 Display(_Root, 0);
}

void Tree ::Display(Node *Cursor, int Depth)
{
 if(Cursor !=NULL)
 {
  Display(Cursor -> Get_RChild(), Depth +1);
  
  for(int i =0; i <Depth; i++)
   cout <<" ";
  
  cout <<Cursor -> GetData() <<endl;
  Display(Cursor -> Get_LChild(), Depth +1);
 }
}