title: Vue.js Multiple definitions of a property not allowed in strict mode
body: <p>Good day.</p>
  
  <p>We are building our application using Vuejs/Vuex/vue-router using the <a href="https://github.com/vuejs/vue-hackernews-2.0" rel="noreferrer">https://github.com/vuejs/vue-hackernews-2.0</a></p>
  
  <p>When building and viewing our application using IE11 we get a <code>SCRIPT1046: Multiple definitions of a property not allowed in strict mode</code> and it references the compiled <code>app.[#hash].js</code> file. I have tracked the duplicate property to the following in the component:</p>
  
  <pre><code>&lt;div class="form-group form-group-list"&gt;
      &lt;label aria-labelledby="Shopping preference"&gt;Shopping preference&lt;/label&gt;
      &lt;ul class="inline"&gt;
          &lt;li&gt;
              &lt;label for="users__secondary_signup__gender__female" aria-labelledby="Gender female"&gt;
                      &lt;span class="enhanced-radio" :class="{ 'selected': selectedGender === 'FEMALE' }"&gt;
                          &lt;input id="users__secondary_signup__gender__female" class="enhance-radio"
                                  :checked="selectedGender === 'FEMALE'" name="gender"
                                  type="radio" value="FEMALE" v-model="selectedGender"&gt;
                      &lt;/span&gt; Female
              &lt;/label&gt;
          &lt;/li&gt;
          &lt;li&gt;
              &lt;label for="users__secondary_signup__gender__male" aria-labelledby="Gender male"&gt;
                      &lt;span class="enhanced-radio" :class="{ 'selected': selectedGender === 'MALE' }"&gt;
                          &lt;input id="users__secondary_signup__gender__male" class="enhance-radio"
                                  :checked="selectedGender === 'MALE'" name="gender"
                                  type="radio" value="MALE" v-model="selectedGender"&gt;
                      &lt;/span&gt; Male
              &lt;/label&gt;
          &lt;/li&gt;
      &lt;/ul&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>The only reference in the compiled file to these are: </p>
  
  <pre><code>domProps: {
      checked: "MALE" === t.selectedGender,
      checked: t._q(t.selectedGender, "MALE")
  },
  and
  domProps: {
      checked: "FEMALE" === t.selectedGender,
      checked: t._q(t.selectedGender, "FEMALE")
  },
  </code></pre>
  
  <p>I cannot find anywhere else in the compiled file where there might be duplicated properties in an object. Has anyone seen this? Are we doing something wrong in the component for it to be doing this?</p>
  
  <p>Thank you, any assistance is appreciated.</p>