private void checkScalar(final String what) {
    checkElt(what);
    if (currentPayloadSize > 0 && payloadByte(0) == 0) {
      throwMalformed("Invalid scalar, has leading zeros bytes");
    }
  }
Sets the input to the item provided (an offset to the beginning of an item) and check this is
valid.

@param item the value to which the current item is to be set.
ethereum/rlp/src/main/java/org/hyperledger/besu/ethereum/rlp/AbstractRLPInput.java