After upgrading jenkins (1.432 to 1.465), the instant-messenger (to 1.21) plugin and the jabber (to 1.22) plugin the jabber comunication (using google talk) stopped working, and started throwing a null pointer exception.

May 26, 2012 6:46:53 PM hudson.plugins.jabber.im.transport.JabberIMConnection connect
INFO: Connected to XMPP on talk.google.com:5222/gmail.com using TLS
May 26, 2012 6:46:53 PM hudson.plugins.jabber.im.transport.JabberIMConnection connect
WARNING: java.lang.NullPointerException
        at hudson.plugins.jabber.im.transport.JabberIMConnection.connect(JabberIMConnection.java:166)
        at hudson.plugins.jabber.im.transport.JabberIMConnectionProvider.createConnection(JabberIMConnectionProvider.java:42)
        at hudson.plugins.im.IMConnectionProvider.create(IMConnectionProvider.java:65)
        at hudson.plugins.im.IMConnectionProvider.access$600(IMConnectionProvider.java:22)
        at hudson.plugins.im.IMConnectionProvider$ConnectorRunnable.run(IMConnectionProvider.java:183)
        at java.lang.Thread.run(Thread.java:662)

In the 1.22 version of the jabber plugin the line where the nullpointer occurs is

 for (IMMessageTarget chat : this.groupChats) {

In the previous version of the jabber plugin I didn´t have any groupChat defined, so I thought that maybe there was some problem updating that configuration so I:

• configured a fake group chat
• saved and restarted (this gave an error that it couldn´t use the groupchat obviously)
• removed the fake group chat
• saved and restarted (now the nullpointer error stopped and everything works fine)

In the end I think that the fix should be either handling the possibility of a null groupchat list or detecting that and fixing the configuration before attempting to connect.