fix: fix disposing sequence

packages/core/src/services/instance/instance.service.ts

@@ -156,7 +156,7 @@ export class UniverInstanceService extends Disposable implements IUniverInstance
  }
 
  private _unitDisposed$ = new Subject<UnitModel>();
- unitDisposed$ = this._unitDisposed$.asObservable();
+ readonly unitDisposed$ = this._unitDisposed$.asObservable();
  getTypeOfUnitDisposed$<T extends UnitModel<object, number>>(type: UniverInstanceType): Observable<T> {
  return this.unitDisposed$.pipe(filter((unit) => unit.type === type)) as Observable<T>;
  }
@@ -242,10 +242,13 @@ export class UniverInstanceService extends Disposable implements IUniverInstance
  const index = units.indexOf(unit);
  units.splice(index, 1);
 
- this._unitDisposed$.next(unit);
+ // Firstly un-mark the unit as "current".
  this._currentUnits$.next({ ...this._currentUnits$.getValue(), [type]: null });
  this._focused$.next(null);
 
+ // Then dispose the unit.
+ this._unitDisposed$.next(unit);
+
  return true;
  }