How to validate if list collector has no value in record producer script

[Dedrei L_]

Please can someone help as I have tried what I think is everything and can't get this to work.  I'm worried I might be going around in circles and stuck focusing on one thing and maybe missing something really straight forward.

What is the correct syntax to validate if a list collector has no value in a record producer script?

currently this is my code:

var clients = "";
clients = producer.u_primary_client.getDisplayValue();
var additionalClients = producer.u_portfolio_list.toString();
if (additionalClients !="")
	{
		  clients += ", " + producer.u_portfolios_list.getDisplayValue();
	}
current.u_clients = clients;

On my form when nothing is selected in u_portfolio_list (list collector) and the field is left completely blank it still enters the IF statement and prints the primary client followed by a comma.

I have tried all of the following:

if (additionalClients !== "")

if (additionalClients !== NULL) and if (additionalClients != NULL)

if (producer.u_portfolio_list.getDisplayValue() !== "")  and if (producer.u_portfolio_list.getDisplayValue() != "")  

if (producer.u_portfolio_list. !== NULL)   and  if (producer.u_portfolio_list. != NULL)

When empty and I print gs.addInfoMessage(producer.u_portfolio_list.toString()) it returns 'undefined' so I have even tried if (producer.u_portfolio_list.toString() == "undefined").

In all these cases the code enters the IF statement and prints the ', '.

Any advice...even if I'm missing something really stupid would be greatly appreciated as this is just doing my head in and wasting sooo much time.

Thanks.

[SanjivMeher]

Can you try

var clients = "";
clients = producer.u_primary_client.getDisplayValue();
if (producer.u_portfolio_list)
	{
		  clients += ", " + producer.u_portfolios_list.getDisplayValue();
	}
current.u_clients = clients;

[Dedrei L_]

That passes by the IF and omits the comma if the field is empty but it also passes the IF statement when there are values selected in the list selector and then doesn't print the , and what has been selected in the list collector.

[SanjivMeher]

Ok. This should work

var clients = "";
clients = producer.u_primary_client.getDisplayValue();
if (producer.u_portfolio_list.toString().length>0)
	{
		  clients += ", " + producer.u_portfolios_list.getDisplayValue();
	}
current.u_clients = clients;

[Dedrei L_]

It does the same, ignores the IF statement when the list collector has no value and also ignores it when it has values.  I also tried 

if (producer.u_portfolio_list.length>0)

without the toString() and that didn't work either.