Fix build.

Author: MKirova

projects/igniteui-angular/src/lib/grids/pivot-grid/pivot-header-row.component.html

@@ -42,7 +42,7 @@
             </div>
             <div #pivotValueContainer [style.min-width.px]="grid.unpinnedWidth" (pointerdown)="$event.preventDefault()"
                 (dropped)="onValueDrop($event, valueArea)" igxDrop
-                (igxDragEnter)="onAreaDragEnter($event, valueArea,undefined)"
+                (igxDragEnter)="onAreaDragEnter($event, valueArea)"
                 (igxDragLeave)="onAreaDragLeave($event, valueArea)">
 
                 <div *ngIf="grid.values.length === 0">

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

@@ -75,7 +75,7 @@ export class IgxPivotHeaderRowComponent extends IgxGridHeaderRowComponent {
         filter.enabled = false;
     }
 
-    public onDimDragOver(event, dimension: PivotDimensionType) {
+    public onDimDragOver(event, dimension?: PivotDimensionType) {
         const typeMismatch = dimension !== undefined ? this.grid.pivotConfiguration.values.find(x => x.member === event.dragChip.id) :
         !this.grid.pivotConfiguration.values.find(x => x.member === event.dragChip.id);
         if (typeMismatch) {
@@ -109,7 +109,7 @@ export class IgxPivotHeaderRowComponent extends IgxGridHeaderRowComponent {
         this._dropPos = DropPosition.AfterDropTarget;
     }
 
-    public onAreaDragEnter(event, area, dimension: PivotDimensionType) {
+    public onAreaDragEnter(event, area, dimension?: PivotDimensionType) {
         const dragId = event.detail.owner.element.nativeElement.parentElement.id;
         const typeMismatch = dimension !== undefined ? this.grid.pivotConfiguration.values.find(x => x.member === dragId) :
         !this.grid.pivotConfiguration.values.find(x => x.member === dragId);