os.date(nil) gives an error instead of acting like os.date()

[technomancy]

• GopherLua is a Lua5.1 implementation. You should be familiar with Lua programming language. Have you read Lua 5.1 reference manual carefully?
• GopherLua is a Lua5.1 implementation. In Lua, to keep it simple, it is more important to remove functionalities rather than to add functionalities unlike other languages . If you are going to introduce some new cool functionalities into the GopherLua code base and the functionalities can be implemented by existing APIs, It should be implemented as a library.

Please answer the following before submitting your issue:

1. What version of GopherLua are you using? : latest from git master
2. What version of Go are you using? : 1.19.3
3. What operating system and processor architecture are you using? : Debian stable on amd64
4. What did you do? : I ran print(os.date(nil))
5. What did you expect to see? : the same thing as if I had run print(os.date())
6. What did you see instead? : <string>:1: bad argument #1 to date (string expected, got nil)

Very minor issue but I thought I'd get it tracked here just for the record.