title: ng-show and ng-model can't work together on the same $scope variable
body: <p>I am trying to have a span element show some $scope variable only if it is not null or empty.</p>
  
  <p>I know i can accomplish this with only ng-model, but i don't understand they this won't work:</p>
  
  <pre><code>&lt;span ng-show="x !== null" ng-model="x"&gt;&lt;/span&gt;
  </code></pre>
  
  <p>or something similar to this.</p>