Object reference not set to an instance of an object (1 Viewer)

[khurram7x]

I've started learning part of XML in VBA and I'm getting the error with a sample code provided in UI Editor for MS Office. It has started after restarting the computer.

I'm pasting error first, plus a screenshot and in the end sample XML from UI Editor:

Thanks,
K

Error:

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

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
at CustomUIEditor.MainForm.ValidateXml(Boolean showValidMessage)
at CustomUIEditor.MainForm.tsbValidateXml_Click(Object sender, EventArgs e)
at System.Windows.Forms.ToolStripItem.RaiseEvent(Object key, EventArgs e)
at System.Windows.Forms.ToolStripItem.HandleClick(EventArgs e)
at System.Windows.Forms.ToolStripItem.HandleMouseUp(MouseEventArgs e)
at System.Windows.Forms.ToolStrip.OnMouseUp(MouseEventArgs mea)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ToolStrip.WndProc(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: 2.0.0.0
Win32 Version: 2.0.50727.5420 (Win7SP1.050727-5400)
CodeBase: file:///C:/Windows/Microsoft.NET/Framework64/v2.0.50727/mscorlib.dll
----------------------------------------
CustomUIEditor
Assembly Version: 3.0.3723.20034
Win32 Version: 3.0.3723.20034
CodeBase: file:///C:/Program%20Files%20(x86)/CustomUIEditor/CustomUIEditor.exe
----------------------------------------
System.Windows.Forms
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.5420 (Win7SP1.050727-5400)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System.Windows.Forms/2.0.0.0__b77a5c561934e089/System.Windows.Forms.dll
----------------------------------------
System
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.5420 (Win7SP1.050727-5400)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System/2.0.0.0__b77a5c561934e089/System.dll
----------------------------------------
System.Drawing
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.5420 (Win7SP1.050727-5400)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System.Drawing/2.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll
----------------------------------------
System.Xml
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.5420 (Win7SP1.050727-5400)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System.Xml/2.0.0.0__b77a5c561934e089/System.Xml.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:

<configuration>
<system.windows.forms jitDebugging="true" />
</configuration>

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.


Code:

<customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui">
<ribbon startFromScratch="true">
<tabs>
<tab id="customTab" label="Contoso" insertAfterMso="TabHomeAccess">
<group idMso="GroupClipboard" />
<group idMso="GroupFontAccess" />
<group id="customGroup" label="Contoso Tools">
<button id="customButton1" label="ConBold" size="large" onAction="conBoldSub" imageMso="Bold" />
<button id="customButton2" label="ConItalic" size="large" onAction="conItalicSub" imageMso="Italic" />
<button id="customButton3" label="ConUnderline" size="large" onAction="conUnderlineSub" imageMso="Underline" />
</group>
</tab>
</tabs>
</ribbon>
</customUI>