fix(virtual-scroll): allow null in items prop (#23047)

Co-authored-by: Robert Rhoades <studioromeo@users.noreply.github.com>

angular/src/directives/virtual-scroll/virtual-scroll.ts

@@ -71,7 +71,7 @@ export declare interface IonVirtualScroll {
    * entire virtual scroll is reset, which is an expensive operation and
    * should be avoided if possible.
    */
-  items?: any[];
+  items?: any[] | null;
 
   /**
    * An optional function that maps each item within their height.