Merge "Handle null values in registerService" into lmp-dev

            for (String key : txtRecords.keySet()) {

                try {

                    // TODO: Send encoded TXT record as bytes once NDC/netd supports binary data.

                    byte[] recordValue = txtRecords.get(key);

                    cmd.appendArg(String.format(Locale.US, "%s=%s", key,

                            new String(txtRecords.get(key), "UTF_8")));

                            recordValue != null ? new String(recordValue, "UTF_8") : ""));

                } catch (UnsupportedEncodingException e) {

                    Slog.e(TAG, "Failed to encode txtRecord " + e);

                }