fix: update when the items changes, fix #866

Author: fncheng

packages/vue-virtual-scroller/src/components/RecycleScroller.vue

@@ -245,7 +245,13 @@ export default {
   },
 
   watch: {
-    items () {
+    items (newItems, oldItems) {
+      if (newItems !== oldItems && newItems.length === oldItems.length) {
+        this.updateVisibleItems(true)
+      }
+    },
+
+    'items.length' () {
       this.updateVisibleItems(true)
     },