NullReferenceException: Object reference not set to an instance of an object

Hello, I am using the code below to read values from xml file.

the issue is : if i use:

 question_TXT.text=reader.GetAttribute("Text");

nothing shows up in the text field.

if i use :

  question_TXT.text=reader.GetAttribute("Text").ToString();

the value shows up in text field but i get NullReferenceException

Thanks

function fillInfo () {

         var reader:XmlTextReader = new XmlTextReader(new StringReader(Malaf2.text));
         // as long as there are info read.
         while(reader.Read())
        {         
 
                  //if the element name= question assign it yo questionText
                 if(reader.Name == "Question")
                  {  
                 // var questionText:Text=question_TXT.GetComponent("Text");
                  //var questionText:Text=GetComponent("UI.Text");
                   //question_TXT.text=reader.GetAttribute("Text");
                   question_TXT.text=reader.GetAttribute("Text").ToString();
                  }
         
        }
     }