SMACK-390 Log exception in parsing extensions of Presence.  Valid Presence will still be returned with extensions missing.

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@13326 b35dd754-fafc-0310-a699-88a17e54d16e
Issue 19. Don't null reader and writer

Conflicts:
	source/org/jivesoftware/smack/XMPPConnection.java