Silence -Wmaybe-uninitialized compiler warnings in dbcommands.c.
When compiling postgres using gcc -O3, there are false-positive
warnings about the now initialized variables. Silence them.
Author: Peter Eisentraut, Andres Freund
Discussion: https://postgr.es/m/
15fb2350-b8b8-e188-278f-
0b34fdee5210@2ndquadrant.com