Slimes don't drop slimeballs.

Slimes don't drop slimeballs in 0.13.0 build 2 Bush 10.0 My Tablet.

To Reproduce
*Go to a world like the flat world and make a fence around the area and spawn the slimes.
*Kill all the slimes and keep trying to get the slimeball but it will not work to get slimeball on Slimes.