Throw exception in sendPacket if packet is null.

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@2151 b35dd754-fafc-0310-a699-88a17e54d16e

source/org/jivesoftware/smack/XMPPConnection.java

@@ -545,6 +545,9 @@ public class XMPPConnection {
         if (!isConnected()) {
             throw new IllegalStateException("Not connected to server.");
         }
+        if (packet == null) {
+            throw new NullPointerException("Packet is null.");
+        }
         packetWriter.sendPacket(packet);
     }