I want,according to user's choices, some fields of my form to be completed. I do that with this code:

2. <script type="text/javascript">
3. $(document).ready(function() {
4. 
   
5. $('#id_veh_id1').bind('click', function () {
6. $('#id_veh_id2').bind('click', function () {
7. 
   
8.  var val1 =$("#id_veh_id1").val();
9.  var val2 =$("#id_veh_id2").val();
10. 
    
11. $.get(""+val1+"/"+val2+"/", function(data) {
12. 
    
13. vlength=data.veh_length;
14. vwidth=data.veh_width;
15. vheight=data.veh_height;
16. v1type=data.v1_type;
17. v2type=data.v2_type;
18. 
    
19. document.getElementById('id_vlength').value=vlength;
20. document.getElementById('id_vwidth').value=vwidth;
21. document.getElementById('id_vheight').value=vheight;
22. document.getElementById('id_type1').value=v1type;
23. document.getElementById('id_type2').value=v2type;
24. });
25. });
26. });
27. });
28. but I can't manage the situation when the user doesn't select anything from the second list. In that case with my code nothing happens. Instead I want only the choice of the first list to be considered and for val2 I want to pass a null/none value. What can I do?
29.