[AttachmentThumbnail] Use other thumbnail when requested isn't available and there's no original file

plugins/StoreRemoteMedia/StoreRemoteMedia.php

@@ -160,6 +160,7 @@ class StoreRemoteMedia extends Plugin
             $attachment = GSFile::storeFileAsAttachment($temp_file);
 
             // Relate the link with the attachment
+            // TODO: Create a function that gets the title from content disposition or URL when such header isn't available
             DB::persist(AttachmentToLink::create([
                 'link_id'       => $link->getId(),
                 'attachment_id' => $attachment->getId(),

src/Entity/AttachmentThumbnail.php

@@ -152,7 +152,7 @@ class AttachmentThumbnail extends Entity
      *
      * @return mixed
      */
-    public static function getOrCreate(Attachment $attachment, ?string $size = null, bool $crop = false)
+    public static function getOrCreate(Attachment $attachment, ?string $size = null, bool $crop = false): ?self
     {
         $size     = $size ?? Common::config('thumbnail', 'default_size');
         $size_int = match ($size) {
@@ -171,7 +171,13 @@ class AttachmentThumbnail extends Entity
             }
             [$predicted_width, $predicted_height] = self::predictScalingValues($attachment->getWidth(), $attachment->getHeight(), $size, $crop);
             if (!file_exists($attachment->getPath())) {
-                throw new NotStoredLocallyException();
+                // Before we quit, check if there's any other thumb
+                $alternative_thumbs = DB::findBy('attachment_thumbnail', ['attachment_id' => $attachment->getId()]);
+                if ($alternative_thumbs === []) {
+                    throw new NotStoredLocallyException();
+                } else {
+                    return $alternative_thumbs[0];
+                }
             }
             $thumbnail              = self::create(['attachment_id' => $attachment->getId()]);
             $mimetype               = $attachment->getMimetype();