09d4438a0d
Base tables that use compact storage may have a special artificial
column that has an empty type.
c010cefc4d fixed the main CDC path to
handle such columns correctly and to not include them in the CDC Log
schema.
This patch makes sure that generation of preimage ignores such empty
column as well.
Fixes #9876
Closes #9910
Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>