Fix .getAttribute on an element without this method

[AnthonySendra]

Hello,

I had an error about object doesn't support property or method 'getAttribute' on IE (mainly Cordova on windows desktop) by clicking on a generated link by <router-link>.

<ul>
     <li>
        <router-link class="MainNav-item" :to="{name: 'ArtistListing'}">
          <span class="MainNav-icon"><icon name="micro"></icon></span>
          Artists
        </router-link>
      </li>
      <li>
        <router-link class="MainNav-item" :to="{name: 'CompetitionListing'}">
          <span class="MainNav-icon"><icon name="cup"></icon></span>
          Competition
        </router-link>
      </li>
</ul>

When you click on the generated link, sometimes in src/components/link.js in the method https://github.com/AnthonySendra/vue-router/blob/d065e37e0e19f399597796b5257bfca3a5c79fd6/src/components/link.js#L85 the e.target can be an instance of SVGElementInstance. But this object does not have the method getAttribute. This error causes the application (Cordova) to crash.

My fix will check if the object (the e.target) has the method getAttribute before calling it.

[posva]

@fnlctrl WDYT?