Index: /CKEditor/trunk/_source/plugins/button/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/button/plugin.js	(revision 3730)
+++ /CKEditor/trunk/_source/plugins/button/plugin.js	(revision 3731)
@@ -189,14 +189,18 @@
 
 		var element = CKEDITOR.document.getById( this._.id );
-		element.setState( state );
-
-		var htmlTitle = this.title,
-			unavailable = this._.editor.lang.common.unavailable,
-			labelElement = element.getChild( 1 );
-
-		if ( state == CKEDITOR.TRISTATE_DISABLED )
-			htmlTitle = unavailable.replace( '%1', this.title );
-
-		labelElement.setHtml( htmlTitle );
+
+		if ( element )
+		{
+			element.setState( state );
+
+			var htmlTitle = this.title,
+				unavailable = this._.editor.lang.common.unavailable,
+				labelElement = element.getChild( 1 );
+
+			if ( state == CKEDITOR.TRISTATE_DISABLED )
+				htmlTitle = unavailable.replace( '%1', this.title );
+
+			labelElement.setHtml( htmlTitle );
+		}
 
 		this._.state = state;