Looks like I stumbled across a typing error in the standard library: "_build > dependencies\wurstStdlib2 > wurst > _wurst > assets > AbilityIds.wurst".
The ability id for itemArmorBonus 'AIde' does not exist in warcraft 3.
It probably should be one of these: 'AId0' to 'AId5', 'AId7' or 'AId8'
Also:
The public class AbilityDefinitionAIde in "_build > dependencies\wurstStdlib2 > wurst > objediting > AbilityObjEditing.wurst" should be renamed to AbilityDefinitionArmorBonus or AbilityDefinitionDefenceBonus to match with AbilityDefinitionAttackBonus (or just add a new class, but I don't think anybody uses the old class [it doesn't work because of the above typo]).