stick to the old fashioned way for testing environment variables

.gitlab-ci.yml

@@ -177,7 +177,7 @@ variables:
 .patch_version: &patch_version
   before_script:
 
-    - if [ -n ${CI_COMMIT_TAG+set} ]; then
+    - if [[ "x$CI_COMMIT_TAG" != "x" ]]; then
         echo "Release detected - patching version - $CI_COMMIT_REF_NAME";
         python -c "import fsl.version as v; v.patchVersion('fsl/version.py', '$CI_COMMIT_REF_NAME')";
       fi