I would rather say that \u003cnil\u003e is the encoded version of <nil>. Could you please give a little bit more info about the configuration of Cells that you use, so that we might help to fix this driver issue?
Just for you to know, I’ve fixed a few issues today for next patch release and among others the one that had thrown the error you reported.
It was an initialisation issue for a scheduler task that archive change events. This happens when the base is empty.
That means that we will have to investigate in another direction to solve your issue when you are back.
Until there, I hope your enjoy your holidays!