title: vuetify combobox getting search string value as input on blur
body: <p>i have a simple v-combobox where i can select/deselect multiple items from a list of object.</p>
  
  <pre><code>&lt;div id="app"&gt;
    &lt;v-app&gt;
      &lt;v-layout column&gt;
        &lt;v-form v-model="valid"&gt;
          &lt;v-combobox
            v-model="selectedItems"
            item-text="name"
            item-value="id"
            :items="itemsList"
            label="Items"
            multiple
            clerable
            persistent-hint
            chips&gt;
            &lt;/v-combobox&gt;
          &lt;div&gt;{{selectedItems}}&lt;/div&gt;
          &lt;/v-form&gt;
       &lt;/v-layout&gt;
    &lt;/v-app&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p><a href="https://codepen.io/anon/pen/pYjZaN" rel="nofollow noreferrer">https://codepen.io/anon/pen/pYjZaN</a>
  The problem is when i write a search string in the field and then click outside i get a chip with it instead of just doing nothing.
  It looks like it depend on v-form, removing it everything will work fine.
  Anyone know how to deal with this?</p>