Include error element in #toXML. SMACK-50

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@2468 b35dd754-fafc-0310-a699-88a17e54d16e

source/org/jivesoftware/smack/packet/Presence.java

@@ -195,6 +195,12 @@ public class Presence extends Packet {
 
         buf.append(this.getExtensionsXML());
 
+        // Add the error sub-packet, if there is one.
+        XMPPError error = getError();
+        if (error != null) {
+            buf.append(error.toXML());
+        }
+
         buf.append("</presence>");
         
         return buf.toString();