When doing /particle blockcrack_id_blockdata the message in Previous Output says "An unknown error occurred while attempting to perform this command"
Steps to reproduce:
1. Type: /give @p command_block
2. Place the command block and put a button on it.
3. In the command block type: /particle blockcrack_2_0 ~ ~1 ~ 1 1 1 1
4. Push the button.
5. Open the command block and read "Previous Output"
The screenshot is taken in 14w29b
Please do not mark unreleased versions (anything starting with "Future Version") as affected. You don't have access to them yet.