This line triggers if the database contents aren't ready yet. I'd say we have three options in that scenario:
1. Always block the site
2. Always allow the site
3. Wait for the DB to be ready
Given that the vast majority of pages aren't malicious, always blocking the site isn't a reasonable default. Also, given the speed of database initialization (an extra network round trip in the worst case), we don't want to wait for the DB to be ready. So that leaves failing open and allowing the site as the right behavior.
If you're having trouble getting the DB to initialize, that's a different problem than the choices on this one if statement.