#vulnerable code 
                                @Override
    public @Nullable Tokens read(ExpressionParser main, Tokens source) {
        Tokens selected = SubparserUtils.readSeparated(main, source, ARRAY_SEPARATORS, SubparserUtils.NAMES_FILTER, MatchableDistributor::hasNext);

        MatchableDistributor matchable = new MatchableDistributor(new TokenDistributor(source));
        matchable.getDistributor().setIndex(selected != null ? selected.size() : 0);

        // at least 4 elements required: <field/variable> [ <index> ]
        if ((source.size() - matchable.getIndex()) < 4) {
            return null;
        }

        // read field name
        matchable.nextVerified();

        // check if the opening section is the square bracket
        if (!matchable.nextVerified().contentEquals(Separators.SQUARE_BRACKET_LEFT)) {
            return null;
        }

        // parameters content
        while (matchable.hasNext() && !matchable.isMatchable()) {
            matchable.nextVerified();
        }

        // check if the [ ] section is closed
        if (!matchable.isMatchable()) {
            return null;
        }

        // check if the closing character was square brace
        if (!matchable.current().contentEquals(Separators.SQUARE_BRACKET_RIGHT)) {
            return null;
        }

        selected = source.subSource(0, matchable.getIndex() + 1);

        // at least 4 elements required: <field-name> [ <index> ]
        if (selected == null || selected.size() < 4 ) {
            return null;
        }

        // array value source has to end with parenthesis
        if (!selected.getLast().contentEquals(Separators.SQUARE_BRACKET_RIGHT)) {
            return null;
        }

        return selected;
    } 
                            #location 32 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public @Nullable Tokens read(ExpressionParser main, Tokens source) {
        SourceStream stream = new PandaSourceStream(source);

        ExpressionSubparsers subparsers = main.getSubparsers().fork();
        subparsers.removeSubparser(getName());

        ExpressionParser parser = new ExpressionParser(main, subparsers);
        Tokens value = parser.read(stream);

        if (TokensUtils.isEmpty(value)) {
            return null;
        }

        MatchableDistributor matchable = new MatchableDistributor(new TokenDistributor(source));
        matchable.getDistributor().setIndex(source.size() - stream.getUnreadLength());

        // at least 3 elements required: [ <index> ]
        if ((source.size() - matchable.getIndex()) < 3) {
            return null;
        }

        // check if the opening section is the square bracket
        if (!matchable.nextVerified().contentEquals(Separators.SQUARE_BRACKET_LEFT)) {
            return null;
        }

        // parameters content
        while (matchable.hasNext() && !matchable.isMatchable()) {
            matchable.nextVerified();
        }

        // check if the [ ] section is closed
        if (!matchable.isMatchable()) {
            return null;
        }

        // check if the closing character was square brace
        if (!matchable.current().contentEquals(Separators.SQUARE_BRACKET_RIGHT)) {
            return null;
        }

        Tokens selected = source.subSource(0, matchable.getIndex() + 1);

        // at least 4 elements required: <field-name> [ <index> ]
        if (selected == null || selected.size() < 4 ) {
            return null;
        }

        // array value source has to end with parenthesis
        if (!selected.getLast().contentEquals(Separators.SQUARE_BRACKET_RIGHT)) {
            return null;
        }

        return selected;
    }