When a miner finds a new block they have to "make" a new transaction and "pay" themselves the reward. The amount of that reward can be from 0 up to the maximum allowed by the block reward based on its height + the total amount of fees of the transactions included in that block. In other words it can also be 0 which is what happened here.

In this case, this block is found by a miner who has been doing "merge mining". What that means is that while the miner works to find a bitcoin block, they can find hashes that satisfy the other altcoin's difficulty and be a valid hash for their block, so they find a block of that altcoin too. In this case the miner was merge mining RSK (rootstock), and to do that you have to add that extra hash you found as a new output in that special transaction (the coinbase tx) with this format: RSKBLOCK:<32 byte hash>. This miner, instead of adding that as a new output, added it as the only output and with a bad format too so he lost the reward (>$48k at current price) of that block he just found.