Hi all whats wrong with this script? getting Uncaught TypeError: Cannot set properties of null (setting 'onchange') Thanks

IsLegalPerson=document.getElementById('IsLegalPerson');
    org=document.getElementById('org');
    inp_org=document.getElementById('CustomerOrganization');
    IsLegalPerson.onchange=function(){
        if(this.value=='true')org.style.display='block';
        else org.style.display='none';
    };
    
    document.body.init_checkout=initListeners;
    document.body.updated_checkout=initListeners;
    function initListeners(){

      var btn = document.querySelector('#place_order');
      if (!btn) return
      
      btn.addEventListener('click', function(e){
        if(IsLegalPerson.value=='false'&&inp_org.value==''){
            e.preventDefault();
        
            inp_org.value='tmp_value';
            btn.click();
        }   
      })
      
    }