pgsql: Robustify tuplesort's free_sort_tuple function

Robustify tuplesort's free_sort_tuple function

41469253e went to the trouble of removing a theoretical bug from
free_sort_tuple by checking if the tuple was NULL before freeing it. Let's
make this a little more robust by also setting the tuple to NULL so that
should we be called again we won't end up doing a pfree on the already
pfree'd tuple. Per advice from Tom Lane.

Discussion: https://postgr.es/m/3188192.1626136953@sss.pgh.pa.us
Backpatch-through: 9.6, same as 41469253e

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5bd38d2f2846c7e387d04a16c4372da0de7b1221

Modified Files
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src/backend/utils/sort/tuplesort.c | 1 +
1 file changed, 1 insertion(+)