Setting a nil key is not an error.

[milochristiansen]

Currently the low-level table code is "error free", as in it does not error out, ever. This makes it easier to write some parts of the VM, but unfortunately the reference VM errors out when you set a nil key.

I either need to check for nil keys in the higher level code with more consistency, or I need to allow the low level code to error out and make sure all areas where the low level table API is used are error safe.