MDL-33681 course: cannot have a section called '0'.

No reason to prevent this. It is just a matter of doing a proper test,
rather than the sloppy PHP !empty().

course/format/topics/lib.php

@@ -69,7 +69,7 @@ function callback_topics_request_key() {
 
 function callback_topics_get_section_name($course, $section) {
     // We can't add a node without any text
-    if (!empty($section->name)) {
+    if ((string)$section->name !== '') {
         return format_string($section->name, true, array('context' => get_context_instance(CONTEXT_COURSE, $course->id)));
     } else if ($section->section == 0) {
         return get_string('section0name', 'format_topics');
@@ -100,4 +100,4 @@ function callback_topics_ajax_support() {
  */
 function callback_topics_get_section_url($courseid, $sectionnum) {
     return new moodle_url('/course/view.php', array('id' => $courseid, 'topic' => $sectionnum));
-}
+}

course/format/weeks/lib.php

@@ -76,7 +76,7 @@ function callback_weeks_request_key() {
  */
 function callback_weeks_get_section_name($course, $section) {
     // We can't add a node without text
-    if (!empty($section->name)) {
+    if ((string)$section->name !== '') {
         // Return the name the user set
         return format_string($section->name, true, array('context' => get_context_instance(CONTEXT_COURSE, $course->id)));
     } else if ($section->section == 0) {