pgsql: Fix allocation check to test the right variable

Fix allocation check to test the right variable

The memory allocation for cancelConn->be_cancel_key was accidentally
checking the be_cancel_key member in the conn object instead of the
one in cancelConn.

Author: Ranier Vilela <ranier.vf@gmail.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: /messages/by-id/CAEudQAq4ySDR6dsg9xwurBXwud02hX7XCOZZAcZx-JMn6A06nA@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/917c00d761fa9ba3b2bc365804ef38fc60ec023e

Modified Files
--------------
src/interfaces/libpq/fe-cancel.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)