MDL-84351 tool_mfa: Fix guidance page file access

File uploaded to the guidance page were not accessible due to
null values being provided to $course and $cm params for the
tool_mfa_pluginfile.

admin/tool/mfa/lib.php

@@ -126,8 +126,8 @@ function tool_mfa_bulk_user_actions(): array {
 /**
  * Serves any files for the guidance page.
  *
- * @param stdClass $course
- * @param stdClass $cm
+ * @param stdClass|null $course
+ * @param stdClass|null $cm
  * @param context $context
  * @param string $filearea
  * @param array $args
@@ -135,7 +135,7 @@ function tool_mfa_bulk_user_actions(): array {
  * @param array $options
  * @return bool
  */
-function tool_mfa_pluginfile(stdClass $course, stdClass $cm, context $context, string $filearea,
+function tool_mfa_pluginfile(stdClass|null $course, stdClass|null $cm, context $context, string $filearea,
     array $args, bool $forcedownload, array $options = []): bool {
     // Hardcode to only send guidance files from the top level.
     $fs = get_file_storage();