pgsql: Don't call CheckAttributeType() with InvalidOid on dropped cols

Don't call CheckAttributeType() with InvalidOid on dropped cols

If CheckAttributeType() is called with InvalidOid, it performs a bunch
of pointless, futile syscache lookups with InvalidOid, but ultimately
tolerates it and has no effect. We were calling it with InvalidOid on
dropped columns, but it seems accidental that it works, so let's stop
doing it.

Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://www.postgresql.org/message-id/93ce56cd-02a6-4db1-8224-c8999372facc@iki.fi
Backpatch-through: 14

Branch
------
REL_18_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/01db3f0398fd2e75569473fc910de5d76d1088b7

Modified Files
--------------
src/backend/catalog/heap.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)