fix(data-warehouse): Removed error being thrown for missing columns

[Gilbert09]

Problem

• We throw an error if there are no columns defined in a data warehouse table when creating the hogql_database
• This is an issue because during data ingestion in warehouse, a table will have no columns defined for a short while, thus, during that period, creating a HogQL Database fails
• Seen in this Sentry ticket

Changes

• Don't throw an error, but just fallback to empty columns

Does this work well for both Cloud and self-hosted?

• Yes