Improve deleting pubkeys.

ox.go

@@ -38,9 +38,18 @@ func oxDeleteNodes(jid string, client *xmpp.Client,
 		return err
 	}
 	query = nodeListReply.SelectElement("query")
+	if query == nil {
+		return errors.New("error parsing iq reply")
+	}
 	items := query.SelectElements("item")
+	if items == nil {
+		return errors.New("error parsing iq reply")
+	}
 	for _, item := range items {
 		node := item.SelectAttr("node")
+		if node == nil {
+			continue
+		}
 		if !strings.Contains(node.Value, nsOx) {
 			continue
 		}