Index: lams_central/web/includes/javascript/addLesson.js
===================================================================
diff -u -r4f284603a74199f14d9eb0d5e1cc04b89755ba31 -r891889896d33e45b8e11594982a8b45d6a503530
--- lams_central/web/includes/javascript/addLesson.js	(.../addLesson.js)	(revision 4f284603a74199f14d9eb0d5e1cc04b89755ba31)
+++ lams_central/web/includes/javascript/addLesson.js	(.../addLesson.js)	(revision 891889896d33e45b8e11594982a8b45d6a503530)
@@ -51,12 +51,14 @@
 		return firstNode && firstNode.data.isDummy;
 	});
 	
-	$.each(emptyFolderNodes, function(){
-		this.setDynamicLoad(function(node, callback){
-			tree.removeChildren(node);
-			callback();
+	if (emptyFolderNodes) {
+		$.each(emptyFolderNodes, function(){
+			this.setDynamicLoad(function(node, callback){
+				tree.removeChildren(node);
+				callback();
+			});
 		});
-	});
+	}
 	
 	tree.getRoot().children[0].expand();
 }