Choose random item off of values?

Error: ServerScriptService.Script:20: bad argument #2 to 'random' (interval is empty)

I am trying to make it so it spawns random blocks if the depth is inbetween their maxdepth and minimumdepth

local material = game.ReplicatedStorage:WaitForChild("Blocks"):GetChildren()
local dt = {}

function makeMine(m,a)
	for i = a,1,-1 do 
		wait()
		for i,v in pairs(m:GetChildren()) do
			if v:IsA("BasePart") then
				if v.Name ~= "Spawned" then
					tick()
					local depth = v.Position.Y
					local dt = {}
					for i,x in pairs(game.ReplicatedStorage.Blocks:GetChildren()) do
						if x.MaxDepth.Value > depth then
							if x.MinimumDepth.Value < depth then
								table.insert(dt,x.Name)
							end
						end
					end
					local random2 = dt[math.random(1,#dt)]
					local randomx = game.ReplicatedStorage.Blocks:FindFirstChild(random2)
					local n = v:Clone()
					n.Parent = m
					n.Position = v.Position - Vector3.new(0,v.Size.Y,0)
					n.BrickColor = randomx.BColor.Value
					n.Material = randomx.BMat.Value
					v.Name = "Spawned"
				end
			end
		end
	end
end

while true do
	workspace.Mine:Destroy()
	local m = game.ReplicatedStorage.Mine:Clone()
	m.Parent = workspace
	makeMine(m,15)
	wait(160)
end