Fix an oversight in refactoring in
06b10f80ba4.
It was against intended skipping prechecking keys optimization in the
first page of range queries to not influence point queries performance.
Reported-by: Anton Melnikov
Discussion: https://postgr.es/m/
30cd7524-b9f1-4cf8-9c4a-
223eb2e34441%40postgrespro.ru
Author: Pavel Borisov