need help with the default gitlab auto devops process. i am using gitlab 12.8.5 by docker, and minikube v1.8.1. when i follow the quick start guide i stuck in the auto build process, bellow is the screenshot: invalid reference format

 Checking out 901de3a8 as master...
 Skipping Git submodules setup
$ if [[ -z "$CI_COMMIT_TAG" ]]; then # collapsed multi-line command
00:03
 $ /build/build.sh
 Building Heroku-based application using gliderlabs/herokuish docker image...
 invalid reference format
 invalid reference format
 invalid argument "/master:901de3a8bd5573f4a049b1457d28bc1592ba6bf9" for "-t, --tag" flag: invalid reference format
 See 'docker build --help'.
 ERROR: Job failed: command terminated with exit code 1

also i have found some similar questions here :

• GitLab CI invalid argument on job for Docker build
• GitLab default autodevops CI: invalid tag name
• GitLab Auto DevOps Failure - Invalid Reference Format

however, i still can't find the solution. please help,thinks.

Billy