Can't update WP -- seems to be missing version number?

I just realized today that my WordPress has not displayed any new plugin updates or the new WP 5.x update. When I visit the update-core.php in the admin, I see this:

If you need to re-install version –, you can do so here

You see it has a dash instead of the version number? That is probably related to the problem... how can I troubleshoot and fix this?

It also says "Last checked on December 14, 2018 at 9:19 am." which is the time right now... so it seems to be checking but it is not returning accurate details back about an update.