title: Element UI - VueJS - Select Input Double Tap bug on IOS
body: <p>I have a weird issue on iOS safari or chrome, when trying to select an option from a select input, when i touch the selector, it shows the options correctly on first tap, but then when i try to select an option, i have to tap twice to make it work, this is my actual scenario:</p>
  
  <pre><code>"element-ui": "^2.13.1", "vue": "^2.6.11"
  </code></pre>
  
  <p>Here is my select input:</p>
  
  <pre><code>                        &lt;el-select class="select-danger"
                                     placeholder="Language / Idioma"
                                     v-model="locale"&gt;
                              &lt;el-option v-for="option in selects.languages"
                                         class="select-danger"
                                         :value="option.value"
                                         :label="option.label"
                                         :key="option.label"&gt;
                              &lt;/el-option&gt;
                          &lt;/el-select&gt;
  
  
  watch: {
        // watch for locale changes
        locale: function (value) {
            alert("selected")
        }
    },
  </code></pre>
  
  <p>This issue seems to happens only on iOS, i tested on android chrome browser and works flawless.</p>
  
  <p>Any ideas of what could be causing this issue?</p>