Not happening. If you compile something to Lua assigning a key to nil will erase it, python and javascript will keep it. Pheraps making a special NullObject value to fill these slots would be a good idea, but you could not interact seamlessly with the target system and probably get a speed penalty.

Having the exact behavoir in all platforms is not possible in some cases, and these are the cases left 'undefined' in the handbook.

Hope this clears things a bit ;)

Cheers, -Shogun