[TYPO3-mvc] Adding relation FE problem

[Henjo Hoeksma]

Hi list,

I am probably overlooking something here, but I keep staring at it 
without luck.

I am adding a relation between two objects in my controller, like so:

$newSubscription->addEvent($event);

While in the BE the TCA does it work nicely and everything is added 
perfectly somehow something is missing in the query that wants to 
insert the relation. FE gives me this error:

You have an error in your SQL syntax; check the manual that corresponds 
to your MySQL server version for the right syntax to use near ' pid) 
VALUES ('16', '1', '1', '24')' at line 1

Understandable since the third argument is missing:

INSERT INTO tx_eventsmanager_event_subscription_mm (uid_foreign, 
uid_local, , pid) VALUES ('16', '1', '1', '24')


What should this 3d argument be?
How to solve this?

Thanks in advance for your suggestions!

Henjo