fix(virtual-scroll): supports null records

fixes 11093

Author: manucorporat

src/components/slides/swiper/swiper.ts

@@ -892,7 +892,7 @@ export function enableTouchControl(s: Slides) {
 // Cleanup dynamic styles
 function cleanupStyles(s: Slides) {
   if (!s.container || !s._wrapper) {
-    //fix #10830
+    // fix #10830
     return;
   }
 

src/components/virtual-scroll/virtual-util.ts

@@ -21,7 +21,7 @@ export function processRecords(stopAtHeight: number,
   let startRecordIndex: number;
   let previousCell: VirtualCell;
   let tmpData: any;
-  let lastRecordIndex = (records.length - 1);
+  let lastRecordIndex = records ? (records.length - 1) : -1;
 
   if (cells.length) {
     // we already have cells
@@ -131,11 +131,11 @@ export function populateNodeData(startCellIndex: number, endCellIndex: number, v
                                  cells: VirtualCell[], records: any[], nodes: VirtualNode[], viewContainer: ViewContainerRef,
                                  itmTmp: TemplateRef<VirtualContext>, hdrTmp: TemplateRef<VirtualContext>, ftrTmp: TemplateRef<VirtualContext>,
                                  initialLoad: boolean): boolean {
-  const recordsLength = records.length;
-  if (!recordsLength) {
+  if (!records || records.length === 0) {
     nodes.length = 0;
     return true;
   }
+  const recordsLength = records.length;
 
   let hasChanges = false;
   let node: VirtualNode;