[bugfix] Picker：incorrect option height in some android devices (#1449)

[bugfix] Picker：incorrect option height in some android devices

packages/picker/PickerColumn.vue

@@ -11,6 +11,7 @@
     <ul :style="wrapperStyle">
       <li
         v-for="(option, index) in options"
+        :key="index"
         v-html="getOptionText(option)"
         class="van-ellipsis"
         :class="b('item', {
@@ -18,6 +19,7 @@
           selected: index === currentIndex
         })"
         @click="setIndex(index, true)"
+        :style="itemStyle"
       />
     </ul>
   </div>
@@ -96,6 +98,11 @@ export default create({
         transform: `translate3d(0, ${this.offset + this.baseOffset}px, 0)`,
         lineHeight: this.itemHeight + 'px'
       };
+    },
+    itemStyle() {
+      return {
+        height: this.itemHeight + 'px'
+      };
     }
   },