[BUGFIX] Don't load codeMirror if there is no textAreas

Resources/Public/js/Tsref.js

@@ -39,5 +39,9 @@ window.onload = function () {
 	}
 
 	// CodeMirror
-	var myCodeMirror = CodeMirror.fromTextArea(document.getElementById('description'), {mode: 'markdown'});
+	var descriptionTexArea = document.getElementById('description');
+	var myCodeMirror;
+	if (descriptionTexArea) {
+		myCodeMirror = CodeMirror.fromTextArea(descriptionTexArea, {mode: 'markdown'});
+	}
 }