Field Null Validation not working

Field Null Validation not working

Hi All,

Here is my code:

  1. varLeadTime = ((input.Coaching_Start_Date - input.Entry_Date)  /  (1000  *  60  *  60  *  24));
  2. if ((varLeadTime  <  7)  &&  (input.Why_now_Compelling_event_and_timelines_  ==  null))
  3. {
  4.     alert "This is less than 1 week notice.  Please complete the 'Additional Information' section (Why Now?) to help us prioritize.";
  5.     cancel submit;
  6. }

Basically, it is a calculation of how many days notice someone provides for a request.  If it is less than 7 days, the user must complete the field 'input.Why_now_Compelling_event_and_timelines_'/.

The issue I am having is, the form is not detecting that the field is null and allows submission.  The field being checked for null is a multi-line field. 

What am I doing wrong? 

Thanks
KP.