The iddoor attribute is an attribute exclusive to door-type items. It places both halves (bottom and top) of the door block in a vertical space. It is because doors are technically two blocks in size that an item is required to place them properly. Failing to set the iddoor attribute for a door item makes the item effectively worthless.
The proper way to add this attribute is as follows:
You'll need to change the number for the iddoor attribute to the block id of your door block.
Not really a bug, but a bit of interesting behavior. Using a door-type item with an iddoor set to a non-door block will place two blocks, one atop the other. Unfortunately, its use is limited as the bottom block will always be the unnumbered basic version of the block, and the top block will always have a damage value of 8.