[rb]modified cookie method

Author: rpallavisharma

rb/lib/selenium/webdriver/remote/bridge.rb

@@ -390,7 +390,6 @@ def delete_cookie(name)
         end
 
         def cookie(name)
-          raise Error::ArgumentError, 'Cookie name cannot be null or empty' if name.nil? || name.empty?
           execute :get_cookie, name: name
         end