ci: fix release branch being pushed into master

Also fix variable quoting issue in link check build.

.gitlab-ci.yml

@@ -232,7 +232,7 @@ push_master_to_github:
     - chmod 600 ~/.ssh/id_rsa
     - echo -e "Host github.com\n\tStrictHostKeyChecking no\n" >> ~/.ssh/config
     - git remote add github git@github.com:espressif/esp-idf.git
-    - git push --follow-tags github HEAD:master
+    - git push --follow-tags github HEAD
 
 
 deploy_docs:
@@ -270,7 +270,7 @@ check_doc_links:
     - triggers
   script:
     # must be triggered with CHECK_LINKS=Yes, otherwise exit without test
-    - test $CHECK_LINKS = "Yes" || exit 0
+    - test "$CHECK_LINKS" = "Yes" || exit 0
     # can only run on master branch (otherwise the commit is not on Github yet)
     - test "${CI_BUILD_REF_NAME}" = "master" || exit 0
     - cd docs