added the check for negative sec

Author: Cosmicoppai

lib/timeout.rb

@@ -164,6 +164,7 @@ def self.ensure_timeout_thread_created
   # Timeout</tt> into your classes so they have a #timeout method, as well as
   # a module method, so you can call it directly as Timeout.timeout().
   def timeout(sec, klass = nil, message = nil, &block)   #:yield: +sec+
+    raise ArgumentError, "Timeout sec must be a positive number" unless sec.is_a?(Numeric) && sec >= 0
     return yield(sec) if sec == nil or sec.zero?
 
     message ||= "execution expired"