feat(igxTreeGrid): Implements correct paging behavior #6640

Author: 3phase

projects/igniteui-angular/src/lib/grids/tree-grid/tree-grid.pipes.ts

@@ -246,12 +246,16 @@ export class IgxTreeGridPagingPipe implements PipeTransform {
             return collection;
         }
 
-        const len = collection.length;
+        const pinnedRecordsLength = this.gridAPI.grid.pinnedRecordsCount;
+        let perPageAfterPinnedRecs = perPage - pinnedRecordsLength;
+        perPageAfterPinnedRecs = (perPageAfterPinnedRecs < 0) ? 0 : perPageAfterPinnedRecs;
+
+        const len = collection.length - pinnedRecordsLength;
         const totalPages = Math.ceil(len / perPage);
 
         const state = {
             index: (totalPages > 0 && page >= totalPages) ? totalPages - 1 : page,
-            recordsPerPage: perPage
+            recordsPerPage: perPageAfterPinnedRecs
         };
 
         const result: ITreeGridRecord[] = DataUtil.page(cloneArray(collection), state);