Avoid an NPE

        // The user has deleted this word and returned to the previous.  Check that the word in the

        // logUnit matches the expected word.  If so, restore the last log unit committed to be the

        // current logUnit.  I.e., pull out the last LogUnit from all the LogBuffers, and make

        // restore it to mCurrentLogUnit so the new edits are captured with the word.  Optionally

        // dump the contents of mCurrentLogUnit (useful if they contain deletions of the next word

        // that should not be reported to protect user privacy)

        // it the mCurrentLogUnit so the new edits are captured with the word.  Optionally dump the

        // contents of mCurrentLogUnit (useful if they contain deletions of the next word that

        // should not be reported to protect user privacy)

        //

        // Note that we don't use mLastLogUnit here, because it only goes one word back and is only

        // needed for reverts, which only happen one back.

        final LogUnit oldLogUnit = mMainLogBuffer.peekLastLogUnit();

        // Check that expected word matches.

        // Check that expected word matches.  It's ok if both strings are null, because this is the

        // case where the LogUnit is storing a non-word, e.g. a separator.

        if (oldLogUnit != null) {

            final String oldLogUnitWords = oldLogUnit.getWordsAsString();

            // Because the word is stored in the LogUnit with digits scrubbed, the comparison must

            // be made on a scrubbed version of the expectedWord as well.

            if (oldLogUnitWords != null && !oldLogUnitWords.equals(

                    scrubDigitsFromString(expectedWord))) {

                return;

            }

            final String scrubbedExpectedWord = scrubDigitsFromString(expectedWord);

            final String oldLogUnitWords = oldLogUnit.getWordsAsString();

            if (!TextUtils.equals(scrubbedExpectedWord, oldLogUnitWords)) return;

        }

        // Uncommit, merging if necessary.

        return Character.isDigit(codePoint) ? DIGIT_REPLACEMENT_CODEPOINT : codePoint;

    }

    /* package for test */ static String scrubDigitsFromString(String s) {

    /* package for test */ static String scrubDigitsFromString(final String s) {

        if (s == null) return null;

        StringBuilder sb = null;

        final int length = s.length();

        for (int i = 0; i < length; i = s.offsetByCodePoints(i, 1)) {