title: Search for issues with custom field of type "Multi-Checkboxes" not ticked
body: <p>In our Jira we have a custom field of type "Multi-Checkboxes".  How can I search for issues which do not have a checkbox checked?  Issues with nothing checked would do, since this is the only checkbox.</p>
  
  <p>I can search for issues with the checkbox checked with a simple query:</p>
  
  <pre><code>Colour = "Red"
  </code></pre>
  
  <p>But nothing I can think of will find issues where it is not checked.  I have tried the following:</p>
  
  <pre><code>Colour != "Red"
  Colour = ""
  Colour is not "Red"
  Colour not in ("Red")
  </code></pre>