I have a macro called "Boxes" that is calling a Razor script and I have a property on this macro named "ChosenBoxes". On the templates that have this macro added, it is called as such:

<umbraco:Macro ChosenBoxes="[$pageRhsBoxes]" Alias="Boxes" runat="server"></umbraco:Macro>

Now $pageRhsBoxes is an alias for a custom data type utilising a Multi-Node Tree Picker.

The issue I am having is that if no nodes are selected within the multi-node picker for a particular page, then in my macro code, it is always giving me back node ids for nodes selected within the multi-node picker of a parent page. The code is as follows:

@{
    if(Parameter.ChosenBoxes != "")
    {
        string[] boxIds = Parameter.ChosenBoxes.Split(',');
        if (boxIds.Length > 0)
        {
            foreach (string boxId in boxIds)
            {
                Node box = new Node(Convert.ToInt32(boxId));
                switch (box.NodeTypeAlias)
                {
                    case "EnquiryForm":
                        @Library.RenderMacro("RHSEnquiryForm");
                        break;
                    case "RecentNews":
                        @Library.RenderMacro("RightRecentNews");
                        break;
                    case "Downloads":
                        @Library.RenderMacro("RightDownloadList");
                        break;
                }
            }        
        }
    }
 } 

If I debug the script in Visual Studio, I can see that the ChosenBoxes parameter has IDs even if none have been selected in the multi-node picker.

Has anyone come across this before, or have any ideas as to the cause?