Remove useless if condition
We can call GetAttributeCompression() with a NULL argument. It
handles that internally already. This change makes all the callers of
GetAttributeCompression() uniform.
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://www.postgresql.org/message-id/flat/
52a125e4-ff9a-95f5-9f61-
b87cf447e4da@eisentraut.org