Use a more straightforward return style in script rules. Instead of

if cond then
		return true
	else
		return false
	end

just do

	return cond

scripts/smb-enum-users.nse

@@ -124,15 +124,7 @@ require 'smb'
 require 'stdnse'
 
 hostrule = function(host)
-
-	local port = smb.get_port(host)
-
-	if(port == nil) then
-		return false
-	else
-		return true
-	end
-
+	return smb.get_port(host) ~= nil
 end
 
 ---Attempt to enumerate users through SAMR methods. See the file description for more information.