To be pedantically correct, Galaxiom, Chr(0) returns the NUL character, using the US-ASCII name for that particular bit pattern. We might colloquially call it Null, but it really isn't Null, it is NUL.
If Chr(0) actually returned a Null, then you would probably get "Invalid use of null" as an error. Speaking of which, ...
DanielR - you say you get an error and you told us where. But you didn't identify WHICH error you get. Please advise us.