Change explicit reference to id 0 to isAirBlock() check

This should solve potential issues that arise then the player has been within the volume of a dynamic tank with Railcraft's hidden tracking blocks. See MinecraftForge/MinecraftForge#602. I think it could be the underlying reason for #158.
(Note that I haven't been able to test this as I have a hard time getting Mekanism to compile at all, but it's such a simple change I don't think I could have gotten it wrong)