Stopping an event

Hello,

I would like to stop processing events if some condition occurs.

I have matrix object and I would like to not update the db if this matrix contains data that is not valid upon pressing update button.

Currently I put my validation logic in OnFormDataUpdateBefore. If it returns error I set bubble event to false so it stops further processing (specifically it won't fire OnFormDataUpdateAfter where I presume data is persisted into db)

The problem is that with bubble event set to false I got some "internal error occured" error.

What happened?

Thanks in advance

Kamil