if every bitcoin user stops making transactions or because last block was a second ago or the miner rejects all existing transactions (for example because of low fees) a block will still be mined. but it will be an empty block so to speak.
but it won't be exactly empty though. it will be a block containing only 1 transaction and that transaction is called coinbase which contains the block reward only
example: Block #478580
https://blockchain.info/block/0000000000000000001f143fdbada82dca6d87d249d76654f0b6d3534b367d01
this block was found after about 40 seconds from last block.
I found, it was interesting because Mining Pool is rewarded with 12.5 BTC from 1 transaction. but it won't be exactly empty though. it will be a block containing only 1 transaction and that transaction is called coinbase which contains the block reward only
example: Block #478580
https://blockchain.info/block/0000000000000000001f143fdbada82dca6d87d249d76654f0b6d3534b367d01
this block was found after about 40 seconds from last block.
