Fixed NPE, caused by adding a 'null' element to the list of package extensions.

02-20 20:20:30.464 E/AndroidRuntime(14377): FATAL EXCEPTION: Smack Packet Writer (0)
02-20 20:20:30.464 E/AndroidRuntime(14377): java.lang.NullPointerException
02-20 20:20:30.464 E/AndroidRuntime(14377):     at org.jivesoftware.smack.packet.Packet.getExtensionsXML(Packet.java:391)
02-20 20:20:30.464 E/AndroidRuntime(14377):     at org.jivesoftware.smackx.packet.DiscoverInfo.getChildElementXML(DiscoverInfo.java:212)
02-20 20:20:30.464 E/AndroidRuntime(14377):     at org.jivesoftware.smack.packet.IQ.toXML(IQ.java:96)
02-20 20:20:30.464 E/AndroidRuntime(14377):     at org.jivesoftware.smack.PacketWriter.writePackets(PacketWriter.java:195)
02-20 20:20:30.464 E/AndroidRuntime(14377):     at org.jivesoftware.smack.PacketWriter.access$000(PacketWriter.java:40)
02-20 20:20:30.464 E/AndroidRuntime(14377):     at org.jivesoftware.smack.PacketWriter$1.run(PacketWriter.java:76)
Improved EntityCaps NodeInformationProvider logic