added check for parent info before processing child update (ARMmbed#1577

)

source/6LoWPAN/Thread/thread_mle_message_handler.c

@@ -763,7 +763,12 @@ static void thread_parse_child_update_response(protocol_interface_info_entry_t *
     uint8_t status;
     bool leader_data_received;
 
+    if (cur->thread_info->thread_endnode_parent == NULL) {
+        return;
+    }
+
     tr_debug("Child Update Response");
+
     //mle_service_buffer_find
     leader_data_received = thread_leader_data_parse(mle_msg->data_ptr, mle_msg->data_length, &leaderData);
     entry_temp = mle_class_get_entry_by_ll64(cur->id, linkMargin, mle_msg->packet_src_address, false);