Trying to create a superflat world with a layer of cauldrons crashes the client

1. Click "Create New World" from the world selection screen.
2. Click "More World Options"; set world type to superflat; click "Customize".
3. Click "Presets"
4. Edit the string to 2;7,2x3,118;1;village
5. Click "Use Preset"

The client then crashes, with an error report and everything.