Problem when i push RoR 3 project to Heroku

i am a beginner of RoR Developer, I have finished develop my app and want to try to host in Heroku. I have followed the instruction from this link but when i pushed, it end with error "Precompiling assets failed"

The error log is :

   rake aborted!
   Sass::SyntaxError: Invalid CSS after "}": expected selector or at-rule, was "{"version":3,"s..."
     (in /tmp/build_9248b9568679e374d00011e249821515/app/assets/stylesheets/application.css)
   (sass):3915

Full Log : https://ideone.com/x0Dp2z

My Repository : https://github.com/iamkevinhuang/covid/