title: AngularJS filter on empty string
body: <p>I have a simple Angular filter setup between a select and a list.  When a user selects an item from the dropdown, the list is updated to show the matching result.  The problem is that I have a "Select..." option first in the dropdown with no value, and when that is the selected value, all items are shown.  I suppose that makes sense, but I want the opposite.  If the selected option has no value, I don't want to show the list.  Here are some relevant bits, followed by a link to a full fiddle:</p>
  
  <p>The dropdown:</p>
  
  <pre><code>&lt;select class="world-list" ng-model="selectedWorld" ng-options="world.worldId as world.worldName for world in allWorlds"&gt;
      &lt;option value=""&gt;Select...&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>The list:</p>
  
  <pre><code>&lt;ul class="unstyled" id="charList"&gt;
      &lt;li ng-repeat="char in characters | filter:selectedWorld"&gt;
          &lt;a href="#" class="btn btn-block" ng-click="selectChar()"&gt;{{char.charName}} - {{char.charRace}} {{char.charClass}}&lt;/a&gt;
      &lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>And here is a link to the full fiddle, which contains my JSON structures that drives all this:  <a href="http://embed.plnkr.co/6XUmC5efO0Y1BRNLRUig" rel="nofollow">http://embed.plnkr.co/6XUmC5efO0Y1BRNLRUig</a></p>
  
  <p>What I'm trying to do is rather simple, and I'm pretty new to Angular so I'm sure I'm missing something obvious.  Checked the Jabbr room, nobody on.  :(</p>
  
  <p>Anyway, thanks for any and all help!</p>