message: Prevent null pointer when comparing review authors
  (fixes
diff: @@ -21,7 +21,7 @@ module.exports = function productReviews () {
  ).then(
  result => {
  utils.solveIf(challenges.noSqlReviewsChallenge, () => { return result.modified > 1 }) // vuln-code-snippet hide-line
  - utils.solveIf(challenges.forgedReviewChallenge, () => { return user?.data && result.original[0].author !== user.data.email && result.modified === 1 }) // vuln-code-snippet hide-line
  + utils.solveIf(challenges.forgedReviewChallenge, () => { return user?.data && result.original[0] && result.original[0].author !== user.data.email && result.modified === 1 }) // vuln-code-snippet hide-line
  res.json(result)
  }, err => {
  res.status(500).json(err)
  