A recent change changed the macos build to run in release mode
which also changed postgres to be built without assertions.
Since we inherit the assertion setting from postgres this leads
to assertions being disabled for our code as well.
With assertions disabled clang errors on detecting null pointer
dereferences so this patch turns assertions for macos back on.
Since the postgres build is cached this took not effect immediately
and remained unnoticed in the CI run against the PR introducing the
change.
417908f19b