SMACK-415 Added fix for handling the empty tag case.

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/branches/smack_3_3_0@13624 b35dd754-fafc-0310-a699-88a17e54d16e
SMACK-415 Added code that was mistakenly removed to handle optional node attribute

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/branches/smack_3_3_0@13625 b35dd754-fafc-0310-a699-88a17e54d16e
SMACK-437 Replaced 'String.isEmpty()' with 'String.length() > 0'

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/branches/smack_3_3_0@13631 b35dd754-fafc-0310-a699-88a17e54d16e