#vulnerable code 
                                private void checkForLeadingZeroes() {
        Character la1 = chars.lookahead(1);
        Character la2 = chars.lookahead(2);
        if (la1 == '0' && DIGIT.isMatchedBy(la2)) {
            throw new ParseException(
                "Numeric identifier MUST NOT contain leading zeroes"
            );
        }
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private void checkForLeadingZeroes() {
        Character la1 = chars.lookahead(1);
        Character la2 = chars.lookahead(2);
        if (la1 != null && la1 == '0' && DIGIT.isMatchedBy(la2)) {
            throw new ParseException(
                "Numeric identifier MUST NOT contain leading zeroes"
            );
        }
    }