Sand does not update in claims

[lmichaelis]

Observed behaviour:

Sand and gravel don't fall in claims.

Expected behaviour:

Sand and gravel observe gravity and fall to the ground when placed in the air.

Steps to reproduce:

Create a new claim, place sand or gravel in the air, observe it not falling.

[mizarc]

Looks like falling entities was caught as part of the mob griefing check. Should be an easy enough fix to exclude them.