When pressing middle mouse button (pick block) on the ground below all the blocks in creative mode it puts an item in your inventory called "Barrier" and when you close out of the game with the item in your inventory it corrupts the world file as shown in second screenshot its stuck in the building terrain
Environment
Java 1.7.0_67 64-bit
Windows 8.1 Pro 64-bit
This issue is a duplicate of MC-58898. It has been linked to the original bugreport.
Please search before reporting any bugs, as it's likely that one exists already.