The dialogs to add a transaction can be opened without any categories in the database

If there is no categories/payment methods in the database - there is no reason to open the add transaction dialogs.

Do we just not open them with a message?
Or every time the program runs - if there is not at least one category (even if only for one transaction type) and at least one payment method - the user is presented with a form to fill in the missing data?
