Ah, yeah, that'd do it.
The scrip expects at least two ingredients, so it doesn't have a failsafe check for when there's only one in a recipe. For the first two ingredients in a recipe, it checks each item to see if they are an item, weapon, or armor, and then checks $dataItems, $dataWeapons, or $dataArmors depending on what the item was. This is where it adds the actual ingredient item to an array, so it checks the database for that.
The third and fourth ingredients have a check where if they don't exist, it skips that part and doesn't load anything. But since recipes require at least two ingredients, the second ingredient isn't checked in that way.
~Ramza