title: angular-ui and datepicker directive error
body: <p>I am trying the following example/demo and I keep getting this error in my chrome console:</p>
  
  <pre><code>Error: Non-assignable model expression: undefined (directive: datepicker)
  </code></pre>
  
  <p>I dont get any 404s during the execution.</p>
  
  <p>The code used is based on:</p>
  
  <p><a href="http://angular-ui.github.io/bootstrap/#/modal" rel="nofollow">http://angular-ui.github.io/bootstrap/#/modal</a></p>
  
  <p>or </p>
  
  <p><a href="http://plnkr.co/edit/?p=preview" rel="nofollow">http://plnkr.co/edit/?p=preview</a></p>
  
  <p>The code in my modal template: </p>
  
  <pre><code>&lt;pre&gt;Selected date is: &lt;em&gt;{{dt | date:'fullDate' }}&lt;/em&gt;&lt;/pre&gt;
      &lt;div class="well well-small pull-left" ng-model="dt"&gt;
          &lt;datepicker min="minDate" show-weeks="showWeeks"&gt;&lt;/datepicker&gt;
      &lt;/div&gt;
  </code></pre>
  
  
      
  
  
  <p>The code in modal controller:</p>
  
  <pre><code>$scope.today = function () {
          $scope.dt = new Date();
      };
      $scope.today();
  
      $scope.showWeeks = true;
      $scope.toggleWeeks = function () {
          $scope.showWeeks = !$scope.showWeeks;
      };
  
      $scope.toggleMin = function () {
          $scope.minDate = ($scope.minDate) ? null : new Date();
      };
      $scope.toggleMin();
  
      $scope.dateOptions = {
          'year-format': "'yy'",
          'starting-day': 1
      };
  </code></pre>