[FIX] branches as strings

.gitlab-ci.yml

@@ -12,7 +12,7 @@ docker-build-10.0:
     - docker build --pull -f 10.0.Dockerfile -t "$CI_REGISTRY_IMAGE:10.0" .
     - docker push "$CI_REGISTRY_IMAGE:10.0"
   only:
-    - 10.0
+    - "10.0"
 
 docker-build-12.0:
   # Official docker image.
@@ -30,7 +30,7 @@ docker-build-12.0:
     - docker push "$CI_REGISTRY_IMAGE:12.0_ml"
     - docker push "$CI_REGISTRY_IMAGE:12.0_py3.6"
   only:
-    - 12.0
+    - "12.0"
 
 docker-build-14.0:
   # Official docker image.
@@ -44,4 +44,4 @@ docker-build-14.0:
     - docker build --pull -f 14.0.Dockerfile -t "$CI_REGISTRY_IMAGE:14.0" .
     - docker push "$CI_REGISTRY_IMAGE:14.0"
   only:
-    - 14.0
+    - "14.0"