Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 5519)
+++ /CKEditor/trunk/CHANGES.html	(revision 5520)
@@ -96,4 +96,5 @@
 		<li><a href="http://dev.fckeditor.net/ticket/5570">#5570</a> : [IE] First enabling SCAYT blind cursor in editor.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/5741">#5741</a> : Enable SCAYT cause error in multiple editor instances.</li>
+		<li><a href="http://dev.fckeditor.net/ticket/5744">#5744</a> : Remove editor with SCAYT enabled in source mode throws error.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/5719">#5719</a> : [IE] 'change' dialog event should not be triggered when dialog is already closed.</li>
 		<li>Updated the following language files:<ul>
Index: /CKEditor/trunk/_source/plugins/scayt/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/scayt/plugin.js	(revision 5519)
+++ /CKEditor/trunk/_source/plugins/scayt/plugin.js	(revision 5520)
@@ -163,4 +163,9 @@
 				var editor = ev.editor,
 					scayt_instance = plugin.getScayt( editor );
+
+				// SCAYT instance might already get destroyed by mode switch (#5744).
+				if ( !scayt_instance )
+					return;
+
 				delete plugin.instances[ editor.name ];
 				// store a control id for restore a specific scayt control settings