Coincidentally, I ran into the same error today.
It is only happening for a particular module (so far). Other modules are just generating fine. I did a republish of the OML and it's dependencies, that sometimes fixes the "Object reference not set to an instance of an object" found in other procedures. It did not help for this. I may need to try to publish a solution with full recompilation on.
Could you check this as well on your modules, Roberto?
Regards,
Rob