There's no need to check if opt->arg is NULL since defGetString() already
does that and raises an ERROR if it is. Let's just remove that check.
Also, combine the two remaining ERRORs into a single check. It seems
better to give an indication about what sort of values we're looking for
rather than just to state that the value given isn't valid. Make
BUFFER_USAGE_LIMIT uppercase in this ERROR message too. It's already
upper case in one other error message, so make that consistent.
Reported-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/20230411.102335.1643720544536884844.horikyota.ntt@gmail.com
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