Change Active Record Encryption variable check to check for emptiness (#32537)

.env.production.sample

@@ -50,6 +50,7 @@ OTP_SECRET=
 # Must be available (and set to same values) for all server processes
 # These are private/secret values, do not share outside hosting environment
 # Use `bin/rails db:encryption:init` to generate fresh secrets
+# Do not change these secrets once in use, as this would cause data loss and other issues
 # ------------------
 # ACTIVE_RECORD_ENCRYPTION_DETERMINISTIC_KEY=
 # ACTIVE_RECORD_ENCRYPTION_KEY_DERIVATION_SALT=