Getting List reference from object instance and PropertyInfo

I have an instance of a unknown object and I am iterating through it's properties, I must retrieve each instance of each property, currently this is my solution:

private static void WriteMembers(object arg, XmlWriter writer, object[] attributes)
{
    foreach (var property in arg.GetType().GetProperties())
    {
        if (attributes.All(x => x.GetType() != typeof (XmlIgnoreAttribute)))
        {
            if (property.GetIndexParameters().Length > 0)
            {
                //how to get list reference?
            }
            else
            {
                var value = property.GetValue(arg, null);

                if (value != null)
                {
                    WriteMember(value, property.Name, writer, property.GetCustomAttributes(false));
                }
            }
        }
    }
}

But I can't use PropertyInfo.GetValue to get the list reference because it throws TargetParameterCountException since the list has an indexed property.

How can I retrieve the list instance?