How to prevent "Unable to cast double to Content"?

This script bellow is made to preload any assets within a model, and it works when there is just one of each item, but if there is more than on of an item (hat, decal ect.) it gets stuck and just says "ContentProvider:Preload() failed for " "Unable to cast double to Content" How can I prevent this?

local function WaitForAssetsToLoad()
	while (ContentProvider.RequestQueueSize > 0) do
		wait(0.1)
	end
end

local function LoadAssets(AssetList)
	for _, Asset in pairs(AssetList) do
		if Asset.ClassName == "StringValue" then
		ContentProvider:Preload(Asset.Value)
		elseif Asset.ClassName == "Sound" then
		ContentProvider:Preload(Asset.SoundId)
		elseif Asset.ClassName == "Decal" or Asset.ClassName == "Texture" then
		ContentProvider:Preload(Asset.Texture)
		elseif Asset.ClassName == "Animation" then
		ContentProvider:Preload(Asset.AnimationId)
		elseif Asset.ClassName == "Shirt" then
		ContentProvider:Preload(Asset.ShirtTemplate)
		elseif Asset.ClassName == "Pants" then
		ContentProvider:Preload(Asset.PantsTemplate)
		elseif Asset.ClassName == "ShirtGraphic" then
		ContentProvider:Preload(Asset.Graphic)
		elseif Asset.ClassName == "CharacterMesh" or Asset.ClassName == "SpecialMesh" then
		ContentProvider:Preload(Asset.MeshId)
		ContentProvider:Preload(Asset.TextureId)
		elseif Asset.ClassName == "ImageLabel" or Asset.ClassName == "ImageButton" then
		ContentProvider:Preload(Asset.Image)
		else		
		LoadAssets(Asset:GetChildren())
		end
	end	
	WaitForAssetsToLoad()
end