Nil

From REALbasicWiki

Nil is a special value which represent every non-existing object

[edit] Objects

Every object is identified by its address (i.e. its position) in memory. When an object does not exist, the address is set to 0, which is interpreted as a Nil object.

[edit] NilObjectException

If you try to access any method/property/constant from a Nil object, REALbasic will raise a NilObjectException because it is impossible to get data from an object that does not exist.