fix issues in core

core/racing/domain/entities/JoinRequest.ts

@@ -39,12 +39,13 @@ export class JoinRequest implements IEntity<string> {
     const id = props.id && props.id.trim().length > 0 ? props.id : `${props.leagueId}:${props.driverId}`;
     const requestedAt = props.requestedAt ?? new Date();
 
+    const message = props.message;
     return new JoinRequest({
       id,
       leagueId: props.leagueId,
       driverId: props.driverId,
       requestedAt,
-      message: props.message,
+      ...(message !== undefined && { message }),
     });
   }