fix: notify about collapsed / expanded groups

Author: Robert Meyer

packages/gantt/src/gantt-upper.ts

@@ -316,8 +316,8 @@ export abstract class GanttUpper implements OnChanges, OnInit, OnDestroy {
     expandGroups(expanded: boolean) {
         this.groups.forEach((group) => {
             group.setExpand(expanded);
+            this.expandChange.emit(group);
         });
-        this.expandChange.next(null);
         this.cdr.detectChanges();
     }
 

packages/gantt/src/gantt.component.ts

@@ -387,17 +387,17 @@ export class NgxGanttComponent extends GanttUpper implements OnInit, OnChanges,
     override expandGroups(expanded: boolean) {
         this.groups.forEach((group) => {
             group.setExpand(expanded);
+            this.expandChange.emit(group);
         });
 
         this.afterExpand();
-        this.expandChange.next(null);
         this.cdr.detectChanges();
     }
 
     override expandGroup(group: GanttGroupInternal) {
         group.setExpand(!group.expanded);
         this.afterExpand();
-        this.expandChange.emit();
+        this.expandChange.emit(group);
         this.cdr.detectChanges();
     }