Minor - fix php warning

Author: jmontoyaa

main/create_course/add_course.php

@@ -313,7 +313,7 @@ function MM_openBrWindow(theURL, winName, features) { //v2.0
             $params['course_category'] = $category_code;
             $params['course_language'] = $course_language;
             $params['gradebook_model_id'] = isset($course_values['gradebook_model_id']) ? $course_values['gradebook_model_id'] : null;
-            $params['course_template'] = $course_values['course_template'];
+            $params['course_template'] = isset($course_values['course_template']) ? $course_values['course_template'] : '';
 
             include_once api_get_path(SYS_CODE_PATH).'lang/english/trad4all.inc.php';
             $file_to_include = api_get_path(SYS_CODE_PATH).'lang/'.$course_language.'/trad4all.inc.php';