Fixed text widget crashing when text is missing

`<$text text=<<missingVariable>>/>` was crashing

core/modules/widgets/text.js

@@ -30,7 +30,7 @@ TextNodeWidget.prototype.render = function(parent,nextSibling) {
 	this.parentDomNode = parent;
 	this.computeAttributes();
 	this.execute();
-	var text = this.getAttribute("text",this.parseTreeNode.text);
+	var text = this.getAttribute("text",this.parseTreeNode.text || "");
 	text = text.replace(/\r/mg,"");
 	var textNode = this.document.createTextNode(text);
 	parent.insertBefore(textNode,nextSibling);