Milk bucket fills in creative, but then no empty bucket to pick up water/lava.

In creative mode, I expected either an already filled milk bucket (such as with water and lava) or for it to be impossible to obtain milk.

However, if you take the empty bucket (used to pick up placed water or lava) and click and hold on a cow to collect milk, it fills the bucket with milk, rendering it useless to pick up water or lava.

To reproduce:
Open Minecraft PE 0.7.0 alpha
Enter creative mode
Find a cow or use a spawn egg to spawn an adult cow
Click and hold on the cow
Bucket will fill with milk
Place water or lava on the ground
It is now not possible to pick up the water or lava in any way with the bucket.