Merge branch 't/13850'

plugins/wysiwygarea/plugin.js

@@ -508,17 +508,25 @@
 			detach: function() {
 				var editor = this.editor,
 					doc = editor.document,
-					iframe = editor.window.getFrame(),
+					iframe,
 					onResize;
 
+				// Trying to access window's frameElement property on Edge throws an exception
+				// when frame was already removed from DOM. (#13850, #13790)
+				try {
+					iframe =  editor.window.getFrame();
+				} catch ( e ) {}
+
 				framedWysiwyg.baseProto.detach.call( this );
 
 				// Memory leak proof.
 				this.clearCustomData();
 				doc.getDocumentElement().clearCustomData();
 				CKEDITOR.tools.removeFunction( this._.frameLoadedHandler );
 
-				if ( iframe ) {
+				// On IE, iframe is returned even after remove() method is called on it.
+				// Checking if parent is present fixes this issue. (#13850)
+				if ( iframe && iframe.getParent() ) {
 					iframe.clearCustomData();
 					onResize = iframe.removeCustomData( 'onResize' );
 					onResize && onResize.removeListener();