MDL-73052 page: Fix page description when it has only an image

This is as regression of MDL-72413, when description was moved to a
standard module API.
In some cases, when description has only images, it's was not
displayed.

mod/page/view.php

@@ -59,7 +59,7 @@ $PAGE->set_url('/mod/page/view.php', array('id' => $cm->id));
 $options = empty($page->displayoptions) ? [] : (array) unserialize_array($page->displayoptions);
 
 $activityheader = ['hidecompletion' => false];
-if (empty($options['printintro']) || !trim(strip_tags($page->intro))) {
+if (empty($options['printintro'])) {
     $activityheader['description'] = '';
 }