If found several images with the same hash, use the equal one as duplicate not the first one with the hash

boards/models/attachment/__init__.py

@@ -52,8 +52,8 b' class AttachmentManager(models.Manager):'
                     equal = False
                     break
             if equal:
-                attachment = existing[0]
-                return attachment
+                attachment = existing_attachment
+        return attachment
 
 
 class Attachment(models.Model):