Merge branch 't/11597'

CHANGES.md

@@ -5,6 +5,7 @@ CKEditor 4 Changelog
 
 Fixed Issues:
 
+* [#11597](http://dev.ckeditor.com/ticket/11597): [IE11] Fixed: Error thrown when trying to open preview using keyboard.
 * [#11544](http://dev.ckeditor.com/ticket/11544): Placeholders will no longer be upcasted in parents not accepting spans.
 * [#8663](http://dev.ckeditor.com/ticket/8663): Fixed [`element.renameNode()`](http://docs.ckeditor.com/#!/api/CKEDITOR.dom.element-method-renameNode) not clearing [`element.getName()`](http://docs.ckeditor.com/#!/api/CKEDITOR.dom.element-method-getName) cache.
 * [#11574](http://dev.ckeditor.com/ticket/11574): Fixed *Backspace* destroying DOM structure if inline editable is placed in list item.

plugins/preview/plugin.js

@@ -89,7 +89,9 @@
 			var oWindow = window.open( sOpenUrl, null, 'toolbar=yes,location=no,status=yes,menubar=yes,scrollbars=yes,resizable=yes,width=' +
 				iWidth + ',height=' + iHeight + ',left=' + iLeft );
 
-			if ( CKEDITOR.env.ie )
+			// For IE we want to assign whole js stored in ieLocation, but in case of
+			// popup blocker activation oWindow variable will be null. (#11597)
+			if ( CKEDITOR.env.ie && oWindow )
 				oWindow.location = ieLocation;
 
 			if ( !CKEDITOR.env.ie && !CKEDITOR.env.gecko ) {