pgsql: Fix nested NOT operation cleanup in tsquery.

Fix nested NOT operation cleanup in tsquery.

During normalization of tsquery tree it tries to simplify nested NOT
operations but there it's obvioulsy missed that subsequent node could be
a leaf node (value node)

Bug #14245: Segfault on weird to_tsquery
Reported by David Kellum.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/19d290155d084754eeb5ebb2569654da06073ee8

Modified Files
--------------
src/backend/utils/adt/tsquery_cleanup.c |  8 +++++++-
src/test/regress/expected/tsearch.out   | 12 ++++++++++++
src/test/regress/sql/tsearch.sql        |  3 +++
3 files changed, 22 insertions(+), 1 deletion(-)