message: handle empty environment variables
diff: @@ -372,10 +372,10 @@ LAGOON_GIT_BRANCH=${BRANCH}\n\
  fi
  if [ "$BUILD_TYPE" == "pullrequest" ]; then
  - yq write -i /kubectl-build-deploy/values.yaml 'prHeadBranch' $PR_HEAD_BRANCH
  - yq write -i /kubectl-build-deploy/values.yaml 'prBaseBranch' $PR_BASE_BRANCH
  - yq write -i /kubectl-build-deploy/values.yaml 'prTitle' $PR_TITLE
  - yq write -i /kubectl-build-deploy/values.yaml 'prNumber' $PR_NUMBER
  + yq write -i /kubectl-build-deploy/values.yaml 'prHeadBranch' "$PR_HEAD_BRANCH"
  + yq write -i /kubectl-build-deploy/values.yaml 'prBaseBranch' "$PR_BASE_BRANCH"
  + yq write -i /kubectl-build-deploy/values.yaml 'prTitle' "$PR_TITLE"
  + yq write -i /kubectl-build-deploy/values.yaml 'prNumber' "$PR_NUMBER"
  echo -e "\
  LAGOON_PR_HEAD_BRANCH=${PR_HEAD_BRANCH}\n\
  @@ -607,10 +607,10 @@ if [ -z "$MONITORING_URLS"]; then
  MONITORING_URLS="${ROUTE}"
  fi
  -yq write -i /kubectl-build-deploy/values.yaml 'route' $ROUTE
  -yq write -i /kubectl-build-deploy/values.yaml 'routes' $ROUTES
  -yq write -i /kubectl-build-deploy/values.yaml 'autogeneratedRoutes' $AUTOGENERATED_ROUTES
  -yq write -i /kubectl-build-deploy/values.yaml 'monitoringUrls' $MONITORING_URLS
  +yq write -i /kubectl-build-deploy/values.yaml 'route' "$ROUTE"
  +yq write -i /kubectl-build-deploy/values.yaml 'routes' "$ROUTES"
  +yq write -i /kubectl-build-deploy/values.yaml 'autogeneratedRoutes' "$AUTOGENERATED_ROUTES"
  +yq write -i /kubectl-build-deploy/values.yaml 'monitoringUrls' "$MONITORING_URLS"
  echo -e "\
  LAGOON_ROUTE=${ROUTE}\n\
  