Quit application while downloading with www.loadfromcacheordownload makes application crash

First, I have successfully downloaded assets bundles with this function

 using (WWW www = WWW.LoadFromCacheOrDownload(GetUrlFromServer(url), version))
             {
                 // Progress slider
                 GameObject loader = new GameObject();
                 loader.name = "TempAssetBundleLoader";
                 loader.tag = "bundleloader";
                 AssetBundleSlider assetBundleSlider = loader.AddComponent<AssetBundleSlider>();
                 assetBundleSlider.www = www;
 
                 if (_isSlideOn)
                     assetBundleSlider.CreateSlider();

                 yield return www;

                 if (www.error != null)
                     throw new System.Exception("WWW download:" + www.error);
                 Debug.Log("Downloaded bundle");
            }

AssetBundleSlider presents download progress like this:

 void Update()
     {
         if (www != null && !www.isDone && downloadSlider != null)
         {
             int percent = (int)(www.progress * 100);
             
             Debug.Log(percent + " %");
         }
         if (www.progress == 1)
         {
             Destroy(gameObject);
             Destroy(downloadSlider);
         }
     }

When downloading is happening, i try to interrupt it:

• When I quit application on ios and go back, app freezes.

• When I quit application on editor, it prompts "Moving file failed" message. I try to call www.Dispose() on AssetBundleSlider but it makes my editor crashes:

      void OnApplicationQuit()
       {
           if (www != null && !www.isDone)
           {
               www.Dispose();
               www = null;
               System.GC.Collect();
           }
       }
  
  

How can I manage to stop downloading and release downloading caches on application quit?