fix(row-drag): deleting the last row throws error #5300

Author: dafo

projects/igniteui-angular/src/lib/grids/row-drag.directive.ts

@@ -35,6 +35,7 @@ export class IgxRowDragDirective extends IgxDragDirective implements OnDestroy {
     public onPointerDown(event) {
         event.preventDefault();
         this._rowDragStarted = false;
+        this._removeOnDestroy = false;
         super.onPointerDown(event);
     }