Improve shards view

[amotl]

Hi there.

Currently, when navigating to the the "Shards" view, Admin UI should display a message like There are no shards. on an empty database where no tables or shards have been created yet.

While Admin UI expects a zero-length result to display this message, CrateDB returns a result with one record. crate/crate#11089 is the respective issue on its issue tracker.

With kind regards,
Andreas.

[amotl]

The suggestion by @mfussenegger was to use an INNER JOIN here, see crate/crate#11089 (comment).

[seut]

I've changed this from bug to feature as the current shard view is not broken with empty tables. Showing an explicit message that no shards exists is indeed an improvement but current situation is not buggy.