On May 23, according to mempool data, an empty block (a block containing only the block reward Coinbase transaction) was mined at Bitcoin height 844689, only 12 seconds after the previous block.

Miners package empty blocks for economic reasons, as it is the most sensible choice for them. In order to make full use of this time for mining and avoid conflicts with transactions packaged in the parent block, miners cannot fill the block with transactions, meaning they can only attempt to mine empty blocks.