message: fix out of bounds access in matc
  b/247442731
diff: @@ -252,7 +252,13 @@ JsonishValue* JsonishParser::parseString() noexcept {
  JsonishValue* arrValue;
  if (arrLexeme && arrLexeme->getType() == ARRAY_START && (arrValue = parseArray())) {
  delete arrValue;
  - size_t length = mLexemes[mCursor].getStart() - strLexeme->getStart();
  +
  + const JsonLexeme* next = peekNextLexemeType();
  + if (!next) {
  + return nullptr;
  + }
  +
  + size_t length = next->getStart() - strLexeme->getStart();
  tmp = std::string(strLexeme->getStart(), length);
  } else {
  tmp = std::string(strLexeme->getStart(), strLexeme->getSize());
  