title: Get "null" when the field is empty
body: <p>I'm trying to submit a form and get the data stocked in it. So, in javascript, I have something like :</p>
  
  <pre><code>$(".form_itk").submit(function(event){
  
      var formData = $(this).serializeArray();
      //...other variables
  
      $.post("/kohana-v3.3.5/ajax/nouvel_itk",{itk : formData, id_culture : id_culture, id_sol : id_sol, id_region : id_region}
          ).done(function(data){
              console.log(data);
          })
  }
  </code></pre>
  
  <p>Then, the variable <code>formData</code> is sent with ajax to make an insert request. The problem is that I can have empty fields in my form but in that case, I want to get a "null" value. Currently, I get nothing, even if the field doesn't exist. How can I force the value to be "null" ? Or is there an other way to get the data of a form in javascript ?</p>
  
  <p>Thanks in advance !</p>
  
  <p>EDIT :</p>
  
  <p>Let's say I have a simple form in html :</p>
  
  <blockquote>
    <p>name : foo</p>
    
    <p>age : 25</p>
    
    <p>sex : woman</p>
    
    <p>hobbie : (empty)</p>
  </blockquote>
  
  <p>I want to add these data into a database.</p>
  
  <p>So I run my javascript code to get the values of this form and after the <code>serializeArray()</code>, I get something like :</p>
  
  <blockquote>
    <p>0 : Object : foo</p>
    
    <p>1 : Object : 25</p>
    
    <p>2 : Object : woman</p>
  </blockquote>
  
  <p>And that's it ! The "hobbie" field doesn't exist in this array.</p>
  
  <p>After that, when I try to do a database request : </p>
  
  <p>Insert into 'human' set('name','age','sex','hobbies') values('foo','25','woman')</p>
  
  <p>This request can't work, that's why I want to have a "null" instead of nothing.</p>