Modding Help Getting "attempt to index a nil value"

I'm trying to read the Item-Name out of the contained Item of my Scripted-Container.

The Error Code I get is:

Code:

[13:24:24.787] Error: Exception while calling script init: (LuaException) Error code 2, [string "/objects/lantian/lantian_dronerag/lantian_dro..."]:16: attempt to index a nil value (local 'contents')

The Code is:

Code:

function dronesContained()
  local contents = world.containerItems(entity.id())

  if contents[1] then
    if contents[1].name == "lantian_drone" then
      return contents[1].count
    else
      return 0
    end
  else
    return 0
  end
end

Line 16 is: "if contents[1] then"

I'm very thankful for every help.

 

That worked perfectly, thanks!
I already thought contents[1] would also return false if contents wouldn't return a value...