Crash when selecting new item from merchants inventory

[Kronspire]

See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.InvalidCastException: Specified cast is not valid.
at SpellforceDataEditor.SFCFF.category_forms.Control30.OnCellValueChange(Object sender, DataGridViewCellEventArgs e)
at System.Windows.Forms.DataGridView.OnCellValidated(DataGridViewCellEventArgs e)
at System.Windows.Forms.DataGridView.OnCellValidated(DataGridViewCell& dataGridViewCell, Int32 columnIndex, Int32 rowIndex)
at System.Windows.Forms.DataGridView.CommitEdit(DataGridViewCell& dataGridViewCurrentCell, DataGridViewDataErrorContexts context, DataGridViewValidateCellInternal validateCell, Boolean fireCellLeave, Boolean fireCellEnter, Boolean fireRowLeave, Boolean fireRowEnter, Boolean fireLeave)
at System.Windows.Forms.DataGridView.CommitEdit(DataGridViewDataErrorContexts context, Boolean forCurrentCellChange, Boolean forCurrentRowChange)
at System.Windows.Forms.DataGridView.OnCellMouseDown(HitTestInfo hti, Boolean isShiftDown, Boolean isControlDown)
at System.Windows.Forms.DataGridView.OnCellMouseDown(DataGridViewCellMouseEventArgs e)
at System.Windows.Forms.DataGridView.OnMouseDown(MouseEventArgs e)
at System.Windows.Forms.Control.WmMouseDown(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.DataGridView.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

************** Loaded Assemblies **************
mscorlib
Assembly Version: 4.0.0.0
Win32 Version: 4.8.9167.0 built by: NET481REL1LAST_B
CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/mscorlib.dll

SpellforceDataEditor
Assembly Version: 1.0.0.0
Win32 Version: 1.0.0.0
CodeBase: file:///D:/Steam/steamapps/common/Spellforce%20Platinum%20Edition/New%20Editor/SpellforceDataEditor.exe

SFEngine
Assembly Version: 1.0.0.0
Win32 Version: 1.0.0.0
CodeBase: file:///D:/Steam/steamapps/common/Spellforce%20Platinum%20Edition/New%20Editor/SFEngine.DLL

OpenTK
Assembly Version: 3.3.2.0
Win32 Version: 3.3.2
CodeBase: file:///D:/Steam/steamapps/common/Spellforce%20Platinum%20Edition/New%20Editor/OpenTK.DLL

System.Windows.Forms
Assembly Version: 4.0.0.0
Win32 Version: 4.8.9093.0 built by: NET481REL1LAST_C
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Windows.Forms/v4.0_4.0.0.0__b77a5c561934e089/System.Windows.Forms.dll

System
Assembly Version: 4.0.0.0
Win32 Version: 4.8.9166.0 built by: NET481REL1LAST_B
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System/v4.0_4.0.0.0__b77a5c561934e089/System.dll

System.Drawing
Assembly Version: 4.0.0.0
Win32 Version: 4.8.9037.0 built by: NET481REL1
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Drawing/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll

System.Core
Assembly Version: 4.0.0.0
Win32 Version: 4.8.9166.0 built by: NET481REL1LAST_B
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Core/v4.0_4.0.0.0__b77a5c561934e089/System.Core.dll

System.Configuration
Assembly Version: 4.0.0.0
Win32 Version: 4.8.9037.0 built by: NET481REL1
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Configuration/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Configuration.dll

System.Xml
Assembly Version: 4.0.0.0
Win32 Version: 4.8.9037.0 built by: NET481REL1
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/System.Xml/v4.0_4.0.0.0__b77a5c561934e089/System.Xml.dll

Accessibility
Assembly Version: 4.0.0.0
Win32 Version: 4.8.9037.0 built by: NET481REL1
CodeBase: file:///C:/Windows/Microsoft.Net/assembly/GAC_MSIL/Accessibility/v4.0_4.0.0.0__b03f5f7f11d50a3a/Accessibility.dll

************** JIT Debugging **************
To enable just-in-time (JIT) debugging, the .config file for this
application or computer (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.

For example:

When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the computer
rather than be handled by this dialog box.