Json errors on unity 2017 (working on 5.6)

Hello,
I’ve got a working project that misteriously breaks till I’ve upgraded to unity 2017.

I’ve get this error, once I try to load a .json file based on a https server (the json file is correct as the error isn’t triggered in Unity 5):

ERROR: 
UnityEngine.Debug:Log(Object)
c__Iterator2:MoveNext() (at Assets/Scripts/OpenRequest.cs:56)
UnityEngine.SetupCoroutine:InvokeMoveNext(IEnumerator, IntPtr)

and the related code that triggers it:

IEnumerator loadingTable(string createLink, string jsonFile){
		check = false;
		www = new WWW(createLink);
		//Load the data and yield (wait) till it's ready 
		yield return www;
		if (www.error == null)
		{
			//Sucessfully loaded the JSON string
			check = true;
		}
		else
		{
			Debug.Log("ERROR: " + www.error);
		}

	}

Is there something changed in unity2017 about json (i’m using litJson library) ?

Change if www.error compare condition to
if (!string.IsNullOrEmpty(www.error))
{
it works