CandidateAttribute.clone() causes NullPointerException

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What steps will reproduce the problem?
1. Clone SDP attributes of a message (e.g. create a response to a 407 message 
using JainSip). At some point, this will call clone() on an instance of 
CandidateAttribute.

What is the expected output? What do you see instead?
- return a reference to the attribute; 
- clone() always returns null;

What version of the product are you using? On what operating system?
Release 413; building from Eclipse; the operating system is Windows 8.1


Please provide any additional information below.
Replacing “return null;” with “return this;” solved the issue for us

Original issue reported on code.google.com by stefanoa...@gmail.com on 22 Jul 2014 at 1:15