Prevent a null hopper owner causing the server to crash

Currently, the getOwner function can return null which can cause NPEs and outright crashes. This PR adds checks to make sure if the getOwner function returns null then the function will be outright cancelled instead of proceeding and causing fatal NPEs.

Caveat: If the block is null for more than 1 cycle, the null debug added in 28eddfcc38d0d8392987abecf74ab189a0e92b47 will be repeatedly spammed in the console/logs.