pgsql: Avoid uninitialized value error in TAP tests' Cluster->psql

Avoid uninitialized value error in TAP tests' Cluster->psql

If the method is called in scalar context and we didn't pass in a stderr
handle, one won't be created. However, some error paths assume that it
exists, so in this case create a dummy stderr to avoid the resulting
perl error.

Per gripe from Oleg Tselebrovskiy <o.tselebrovskiy@postgrespro.ru> and
adapted from his patch.

Discussion: /messages/by-id/378eac5de4b8ecb5be7bcdf2db9d2c4d@postgrespro.ru

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c3e28e9fd936b83dbb6dfb5003b6221d98f8469c

Modified Files
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src/test/perl/PostgreSQL/Test/Cluster.pm | 8 ++++++++
1 file changed, 8 insertions(+)