Properly keep track of song items (fixes #427)

resources/assets/js/components/shared/song-item.vue

@@ -3,7 +3,6 @@
     class="song-item"
     draggable="true"
     :data-song-id="song.id"
-    key="id"
     @click="$parent.rowClick(song.id, $event)"
     @dblclick.prevent="playRightAwayyyyyyy"
     @dragstart="$parent.dragStart(song.id, $event)"

resources/assets/js/components/shared/song-list.vue

@@ -35,7 +35,7 @@
       </thead>
 
       <tbody>
-        <tr is="song-item" v-for="item in displayedItems" :song="item" ref="rows"/>
+        <tr is="song-item" v-for="item in displayedItems" :song="item" ref="rows" :key="item.id"/>
       </tbody>
     </table>