Block IDs that don't exist as an item crash Superflat customisation GUI.

As you know, some Item IDs are no longer valid, such as 92 (the block ID of a cake - a cake in the inventory is item #354). Using a block ID whose corresponding item ID was removed can cause the Superflat customisation GUI to crash, as the layer entry can't be rendered.
Using the same preset code on a server works just fine... well, until the client starts loading distant chunks.

Please find enclosed the crash report.

What I expected to happen was...:
A name to appear in the graphical list of block layers, along with either a blank icon or some representation of the texture.

What actually happened was...:
A NullPointerException.

Steps to Reproduce:
1. Go to Singleplayer → Create new world → More world options → Customise (with Superflat selected as the world type)
2. Enter the following preset code: 2;92;1; and select Use Preset.