Server Error in '/' Application.

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Line 187:                    if (loadProductDisplay)
Line 188:                    {
Line 189:                        Item_ItemGroup.Merge(iiGTA.GetDataByItemGroupActiveOnly(itemGroup));
Line 190:                        Item.Merge(iTA.GetDataByItemGroupActiveOnly(itemGroup));
Line 191:                        ItemGroup_ItemGroup.Merge(igigTA.GetDataByItemGroup(itemGroup));

[ArgumentNullException: Value cannot be null.
Parameter name: key]
   System.Data.DataTable.RestoreIndexEvents(Boolean forceReset) +262
   System.Data.Merger.MergeTable(DataTable src, DataTable dst) +399
   System.Data.Merger.MergeTableData(DataTable src) +68
   System.Data.Merger.MergeTable(DataTable src) +187
   System.Data.DataTable.Merge(DataTable table, Boolean preserveChanges, MissingSchemaAction missingSchemaAction) +128
   System.Data.DataTable.Merge(DataTable table) +8
   dsProductDisplay.LoadByItemGroup(String itemGroup) in e:\WebSites\HelioWebFront\App_Code\BusinessEntity\dsProductDisplay.cs:189
   bcProduct.LoadItemGroup(String itemGroup) in e:\WebSites\HelioWebFront\App_Code\BusinessComponent\bcProduct.cs:67
   ucGroupItem.Page_Load(Object sender, EventArgs e) in e:\WebSites\HelioWebFront\UserControl\ucGroupItem.ascx.cs:43
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +15
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +33
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +47
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1436