Fix accidental use of = instead of ==
Fix for commit
630f9a43cec. It used = instead of ==. The result
would be an incorrect error message.
Author: Jacob Brazeal <jacob.brazeal@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/flat/CA%2BCOZaC-JMbhQ4O0Q8V1Bxa0R%2BNex_RN9D6UyuLPiEx_CK4Heg%40mail.gmail.com