# Error on pasting element in Expression binding

**URL:** <https://forum.inductiveautomation.com/t/error-on-pasting-element-in-expression-binding/103794>\
**Category:** Ignition\
**Tags:** perspective\
**Created:** [March 17, 2025, 5:54pm UTC](https://forum.inductiveautomation.com/t/error-on-pasting-element-in-expression-binding/103794 "2025-03-17T17:54:05Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![mdemaris](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/mdemaris/32/54639_2.png) [@mdemaris](https://forum.inductiveautomation.com/u/mdemaris)\
**Post date:** [March 17, 2025, 5:54pm UTC](https://forum.inductiveautomation.com/t/error-on-pasting-element-in-expression-binding/103794/1 "2025-03-17T17:54:05Z")

</div>

Hello,

I receive this error when I paste a reference to `root.custom.prop`.

This is the expression binding:  
`concat('New Value: ', {/root.custom.data_out.di_5})`

All I am doing is pasting in a new reference like: `{/root.custom.data_out.user}` to replace the existing one. (No, I am not pasting this exact reference...)

And the error I get in the console: (Twice)

```python
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "com.jidesoft.editor.SyntaxDocument.getLength()" because "this._document" is null
	at com.jidesoft.editor.CodeEditor.offsetToModelPosition(Unknown Source)
	at com.jidesoft.editor.CodeEditor.offsetToViewPosition(Unknown Source)
	at com.jidesoft.editor.CodeEditorPainter.invalidateRange(Unknown Source)
	at com.jidesoft.editor.CodeEditorPainter.invalidateSelectedLines(Unknown Source)
	at com.jidesoft.editor.CodeEditor.blinkCaret(Unknown Source)
	at com.jidesoft.editor.action.InputHandler$a.actionPerformed(Unknown Source)
	at java.desktop/javax.swing.Timer.fireActionPerformed(Unknown Source)
	at java.desktop/javax.swing.Timer$DoPostEvent.run(Unknown Source)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(Unknown Source)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(Unknown Source)
	at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
	at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
	at java.base/java.security.AccessController.doPrivileged(Unknown Source)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
	at java.desktop/java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.desktop/java.awt.EventDispatchThread.run(Unknown Source)

```

UPDATE:  
Now, I only get this error message every time I type in the expression area:

```python
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

```