Fix Possible NPE

            final ArrayList<PendingAttribute> attrList = bigrams.get(entry.getKey());

            if (attrList != null) {

                for (final PendingAttribute attr : attrList) {

                    to.setBigram(word1, unigrams.get(attr.mAddress),

                    final String word2 = unigrams.get(attr.mAddress);

                    if (word1 == null || word2 == null) {

                        Log.e(TAG, "Invalid bigram pair detected: " + word1 + ", " + word2);

                        continue;

                    }

                    to.setBigram(word1, word2,

                            BinaryDictInputOutput.reconstructBigramFrequency(unigramFrequency,

                                    attr.mFrequency));

                }