Im kinda tired of these kind of posts.
Lets analyze your error shall we?

Code:
cannot cast undefined to bool: (file 'maps/mp/gametypes/hns2.gsc', line 1620)
 if(!level.newround)
    *
Now, what the error is saying:
cannot cast undefined to bool

The star indicates what variable cannot be cast to a bool because it's undefined.

the star is under level.newround.

So this tells us

the script throws an error
because
level.newround is undefined
and
it is used as a bool(ean).

You get the picture?

The variable is undefined
and you are trying to use it as a bool

to fix this
define it!