2512941 - XBRL mapper throws error message Object reference not set to an instance of an object.

When opening a chapter and starting the XBRL mapper, we get the following error

Exception Source: SAP.XBRL.AddIn
Exception Type: System.NullReferenceException
Exception Message: Object reference not set to an instance of an object.
Exception Target Site: SynchronizeConceptTreeview

FULL ERROR

Detailed technical information follows:
---
(Inner Exception)
Date and Time: 8/3/2017 11:52:47 AM
Machine Name: BPC10SQL12
IP Address: fe80::b4fe:da4f:9f33:d693%13
Current User: BPC10SQL12\Administrator

Application Domain: C:\Program Files (x86)\SAP\SAP Disclosure Management XBRL Mapper\
Assembly Codebase: file:///C:/Program Files (x86)/SAP/SAP Disclosure Management XBRL Mapper/SAP.XBRL.AddIn.DLL
Assembly Full Name: SAP.XBRL.AddIn, Version=10.1.6.9, Culture=neutral, PublicKeyToken=0d33b164cd90812a
Assembly Version: 10.1.6.9

Exception Source: SAP.XBRL.AddIn
Exception Type: System.NullReferenceException
Exception Message: Object reference not set to an instance of an object.
Exception Target Site: SynchronizeConceptTreeview

---- Stack Trace ----
SAP.XBRL.AddIn.ucMappingController_Excel.SynchronizeConceptTreeview(currentConcepts As List`1, worksheet As Worksheet, mappings As List`1)
ucMappingController_Excel_Synchronize.cs: line 0820, col 21, IL 0171 (0xAB)
SAP.XBRL.AddIn.ucMappingController_Excel.ucTabControl_synchronizeEvent()
ucMappingController_Excel_Synchronize.cs: line 0615, col 17, IL 0275 (0x113)
SAP.XBRL.AddIn.ucTabControl.Synchronize()
ucTabControl.cs: line 0272, col 17, IL 0008 (0x8)
SAP.XBRL.AddIn.ExcelTaskPaneController.Synchronize()
ExcelTaskPaneController.cs: line 0270, col 21, IL 0039 (0x27)
SAP.XBRL.AddIn.ExcelTaskPaneController.adxExcelEvents_SheetSelectionChange(sender As Object, sheet As Object, range As Object)
ExcelTaskPaneController.cs: line 0717, col 13, IL 0045 (0x2D)
AddinExpress.MSO.ADXExcelAppEvents.DoSheetSelectionChange(sheet As Object, range As Object)
SAP.XBRL.AddIn.DLL: N 0017 (0x11) IL

(Outer Exception)
Date and Time: 8/3/2017 11:52:48 AM
Machine Name: BPC10SQL12
IP Address: fe80::b4fe:da4f:9f33:d693%13
Current User: BPC10SQL12\Administrator

Application Domain: C:\Program Files (x86)\SAP\SAP Disclosure Management XBRL Mapper\
Assembly Codebase: file:///C:/Program Files (x86)/SAP/SAP Disclosure Management XBRL Mapper/AddinExpress.MSO.2005.DLL
Assembly Full Name: AddinExpress.MSO.2005, Version=8.1.4350.0, Culture=neutral, PublicKeyToken=4416dd98f0861965
Assembly Version: 8.1.4350.0

Exception Source:
Exception Type: AddinExpress.MSO.ADXExternalException
Exception Message: An error has occurred in the code of the add-in.

---- Stack Trace ----

Disclosure Management

Object reference not set to an instance of an object, XBRL Mapper, Locked excel sheet , KBA , troubleshooting , best practices , EPM-DSM-SEC , DM for US SEC Reporting , Problem