Lookup error with click method

Hi All,

I have a trouble with lookup form.

When I click the button the client always throw an error:

Error::"An unexpected client error has occurred."

And this is the code with I click method:

[Control("Button")]

class btnSelFields

{

client void clicked()

{

Args args;

FormRun formRun;

;

super();

edtTmpExpression.setFocus();

//Client error fixed by Larry 08212017 -->

//args = new Args(formstr(CPRFieldLabelLookup));

args = new Args();

args.name(formstr(CPRFieldLabelLookup));

args.caller(element);

//<--

formRun = classfactory.formRunClass(args);

formRun.init();

edtTmpExpression.performFormLookup(formRun);

}

}

And when I debug into it, it will throw this error message:

TypeError:Unable to get property 'Popup' of undefined or null reference at t.serverForm.InteractionHandler.prototype._handleViewInteractions(Myhost/Scripts/Scripts/dyn-core.min...js:38:19284)

Any one have idea with that?

Thanks