fix(grid): add null check for activeNode

Author: ddaribo

projects/igniteui-angular/src/lib/grids/grid/column-group.spec.ts

@@ -218,9 +218,9 @@ describe('IgxGrid - multi-column headers #grid', () => {
 
             const gridContent = GridFunctions.getGridContent(fixture);
 
-            expect(async () => {
+            expect(() => {
                 gridContent.triggerEventHandler('focus', null);
-                await wait(400);
+                tick(400);
                 fixture.detectChanges();
             }).not.toThrow();
         }));

projects/igniteui-angular/src/lib/grids/headers/grid-header-group.component.ts

@@ -161,7 +161,7 @@ export class IgxGridHeaderGroupComponent implements DoCheck {
      * @hidden
      */
     public get ariaHidden(): boolean {
-        return this.grid.hasColumnGroups && (this.column.hidden || this.grid.navigation.activeNode.row !== -1);
+        return this.grid.hasColumnGroups && (this.column.hidden || this.grid.navigation.activeNode?.row !== -1);
     }
 
     /**

projects/igniteui-angular/src/lib/grids/headers/grid-header-row.component.ts

@@ -118,7 +118,7 @@ export class IgxGridHeaderRowComponent implements DoCheck {
     * @internal
     */
     public get isLeafHeaderAriaHidden(): boolean {
-        return this.grid.navigation.activeNode.row === -1;
+        return this.grid.navigation.activeNode?.row === -1;
     }
 
     /** The virtualized part of the header row containing the unpinned header groups. */