Dispensers don't collect powder snow

Activating a dispenser containing a bucket will not collect powder snow in front of it.

 

Steps to Reproduce:

1. Place a dispenser and put a bucket inside it.
2. Place powder snow in front of the dispenser. 
3. Activate the dispenser using a redstone signal.

 

Observed Results:

Dispenser does not collect powder snow and instead dispenses the bucket. 

 

Expected Results:

Dispenser will collect powder snow and contain a powder bucket.