Dispensed powder snow does not replace grass

Powdered snow will replace grass and ferns when placed by a player, but does not when placed by dispenser. This is unlike the behavior of liquids which can replace grass when dispensed.

To reproduce:
1. Place grass or similar in front of dispenser 
2. Put powdered snow inside dispenser
3. Power dispenser
The powdered snow bucket will be dispensed in item form as if a block is in the way.