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_14_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/d2f58c42a2613cc65cddd7a223f85b6bfc0093fb

Modified Files
--------------
src/backend/catalog/heap.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)