This null script event what is it due to? Is there any phenomenon I am not aware of?
There is no script needed to spend the transaction vout referenced in the input because it was not locked with a key. For example, the txid of the first transaction referenced is
c3d8d15a3ca1b50fc2519cbcb79f1db3b6be164c176c7ad51c7a5ec2e97ffa7b with output index
204. Below is how the that transaction output was locked.
The locking script basically pushes 32 bytes of data onto the stack (
7daba6288bcf43c2f7f555ec58f965eaac89b14bc4c4fc920a2a58163aa11e0e) with no verification opcodes at the end of it. That means, it can be spent with an empty signature. This types of transactions were generally done if you wanted to store hash of some data on the bitcoin blockchain. But that can now be achieved with a OP_RETURN opcode which prevents UTXO bloat. All but the last transaction that has been referenced are coinbase transactions which is paying out fractions of the newly generated bitcoins to the participating miners of the pool. It is possible that the pool manager wanted to encode and store a particular data onto the bitcoin blockchain.