MDL-79276 core: Auto close streaming elements in shutdown handler

lib/classes/shutdown_manager.php

@@ -240,6 +240,9 @@ class core_shutdown_manager {
             }
         }
 
+        // Close the current streaming element if any.
+        echo $OUTPUT->close_element_for_append();
+
         // Print any closing buffered tags.
         if (!empty($CFG->closingtags)) {
             echo $CFG->closingtags;