我用异步加载 会遇到问题：请问什么原因造成的。

The AssetBundle 'L12.unity3d' can't be loaded because another AssetBundle with the same files is already loaded.

if (GetAssetBundle(assetBundlePath) == null)
                    {
                        AssetBundleCreateRequest request = null;
                        try
                        {
                             request = AssetBundle.LoadFromFileAsync(assetBundlePath);
                        }
                        catch
                        {

                        }
                        yield return request;
                        if (request.isDone)
                        {
                            try
                            {
                                AssetBundle temp = request.assetBundle;
                                assetBundleDic.Add(assetBundlePath, temp);
                            }
                            catch
                            {

                            }
                        }
                    }
                    AssetBundle ab = GetAssetBundle(assetBundlePath);
                    AssetBundleRequest abRequest = ab.LoadAssetAsync<Texture>(textureName);
                    yield return abRequest;

                    if (abRequest.isDone)
                    {
                        Texture texture = abRequest.asset as Texture;
                        EventCenter.Broadcast(EventType.SequenceTextureLoaded, texture);
                    }