when is outside the steps

Jenkinsfile

@@ -70,12 +70,12 @@ pipeline {
       }
     }
     stage('Build production deliverable') {
-      steps {
       when {
         expression {
           buildArtifact
         }
       }
+      steps {
         catchError(buildResult: 'FAILURE', stageResult: 'FAILURE') {
           sh ''' #!/usr/local/bin/bash
             ZIP_FILE="url-shortener_${BRANCH_NAME}_$(date "+%Y-%m-%d_%H-%M-%S").tgz"