ChainCatcher message, according to mempool data, miners have mined an empty block at Bitcoin height 871732 (i.e., the block only contains one transaction for the block reward Coinbase), with only a 6-second interval from the previous block height.

Miners pack empty blocks for economic reasons; this is the wisest choice for miners. In order to make full use of this time for mining and to avoid conflicts with transactions packed in the parent block, miners cannot fill the block with transactions, meaning that miners can only attempt to mine empty blocks.