Add null check prior to using object.

modules/islandora_text_extraction/islandora_text_extraction.module

@@ -36,11 +36,18 @@ 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'];
-    $file = File::load($file_id);
-    $data = file_get_contents($file->getFileUri());
-    $data = nl2br($data);
-    $media->set('field_edited_text', $data);
-    $media->field_edited_text->format = 'basic_html';
+    if ($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.");
+    }
   }
 }