Why my Dockerfile causes error at Docker Hub?

I write following Dockerfile:

And autobuild it on Docker Hub:


But it causes an error report “Unexpected error”. However I can pull the image:

$ docker pull masterq/docker4fdb
Using default tag: latest
latest: Pulling from masterq/docker4fdb
22dc81ace0ea: Already exists 
1a8b3c87dba3: Already exists 
91390a1c435a: Already exists 
07844b14977e: Already exists 
b78396653dae: Already exists 
fab389ee740f: Pull complete 
Digest: sha256:39ec1e3799ded1c7cfdfedccfc0561f082f891505269946657a26ca918214865
Status: Downloaded newer image for masterq/docker4fdb:latest

Why does Docker Hub maintain my Dockerfile as error?

Best regards,