Iron Trapdoor has wrong position in creative inventory

The bug

In the creative inventory, the Iron Trapdoor has an incorrect position. The Iron Door is followed by the different Wooden Doors, but the Iron Trapdoor is not followed by the different Wooden Trapdoors, as it would supposed to be.

How to reproduce

1) Switch to creative mode
2) Open the inventory
3) Click the category "Redstone"
4) You see the bug described above