fix: view not unused if item no longer present, fix #774

Author: Akryum

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

@@ -505,7 +505,7 @@ export default {
 
  // Check if index is still in visible range
  if (
- view.nr.index === -1 ||
+ view.nr.index == null ||
  view.nr.index < startIndex ||
  view.nr.index >= endIndex
  ) {