Fix historical info of bigrams reading.

                                if (options.mHasTimestamp) {

                                    probability = buffer.readUnsignedByte();

                                    final int pos = buffer.position();

                                    // Skip historical info.

                                    buffer.position(pos + FormatSpec.BIGRAM_TIMESTAMP_SIZE

                                            + FormatSpec.BIGRAM_LEVEL_SIZE

                                            + FormatSpec.BIGRAM_COUNTER_SIZE);

                                    // Skip timestamp

                                    buffer.readInt();

                                    // Skip level

                                    buffer.readUnsignedByte();

                                    // Skip count

                                    buffer.readUnsignedByte();

                                } else {

                                    probability = bigramFlags

                                            & FormatSpec.FLAG_BIGRAM_SHORTCUT_ATTR_FREQUENCY;