We only go through event creation and calling when dispensing filled buckets
if the bucket is able to place its liquid. However, the check for this is
incorrect so the event is not called when a block liquids can destroy is
in front of the dispenser. This commit fixes the check to match the checks
vanilla does when actually using the bucket.
When an event changes the item to be dispensed we check to see if the new
item has special behavior for dispensing and if so pass it on to that
behavior handler. However, we are actually checking the old itemstack and
passing the new itemstack so this check fails.
