title: Vuetify v-select multiple feature used in tandem with v-data-table has trouble tracking model bindings
body: <p>I have run into some odd behaviour with v-select and v-data-table.  The issue is with model bindings holding the selection of given v-select component when presented for each row in a v-data-table.  It's not clear whether I'm using the input bindings in a way that does not play well with Vuetify (v-select bindings are stored in an object, keyed by ID from each row of the table), or whether this is a legitimate defect with the v-select component.  </p>
  
  <p>The issue only seems to happen when the <code>multiple</code> feature is enabled on a v-select component and is demonstrated by this Codepen:   <a href="https://codepen.io/dkichler/pen/gKBZLR" rel="nofollow noreferrer">https://codepen.io/dkichler/pen/gKBZLR</a></p>
  
  <p>It can be demonstrated by choosing a selection for one of the rows, and then attempting to change the sort order (by Name, for example).  The table using single selection v-selects reorders and maintains selections with the appropriate row, as expected, but the multiple selection v-select table does not, and instead throws a TypeError:</p>
  
  <p><code>[Vue warn]: Error in callback for watcher "inputValue": "TypeError: Cannot read property 'findIndex' of undefined"</code></p>
  
  <p>Am I using the component incorrectly, or is there a defect with the v-select or v-data-table?</p>