Add null check prior to using object. (#791)

modules/islandora_text_extraction/islandora_text_extraction.module

@@ -36,13 +36,20 @@ function islandora_text_extraction_media_presave(MediaInterface $media) {
   $text = $media->get('field_edited_text')->getValue();
   if (!$text) {
     $file_id = $media->get('field_media_file')->getValue()[0]['target_id'];
+    if ($file_id) {
       $file = File::load($file_id);
+      if ($file) {
         $data = file_get_contents($file->getFileUri());
         $data = nl2br($data);
         $media->set('field_edited_text', $data);
         $media->field_edited_text->format = 'basic_html';
       }
     }
+    else {
+      \Drupal::logger('islandora_text_extraction')->warning("No file associated with media entity.");
+    }
+  }
+}
 
 /**
  * Implements hook_media_insert().