pgsql: Guard against null t->tm_zone in strftime.c.

Guard against null t->tm_zone in strftime.c.

The upstream IANA code does not guard against null TM_ZONE pointers in this
function, but in our code there is such a check in the other pre-existing
use of t->tm_zone. We do have some places that set pg_tm.tm_zone to NULL.
I'm not entirely sure it's possible to reach strftime with such a value,
but I'm not sure it isn't either, so be safe.

Per Coverity complaint.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a54d5875fe0bc19d05236b85e1e1bf0af9fa2902

Modified Files
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src/timezone/strftime.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)