stash potential changes in submodule

.gitlab-ci.yml

@@ -62,6 +62,7 @@ build:courses:
     - if: $CI_COMMIT_BRANCH == "develop"
     - if: $CI_COMMIT_BRANCH == "master"
   before_script:
+    - git submodule foreach 'git stash'
     - git submodule update --init --recursive
   script:
     - bash .ci/deploy.sh