Fix empty TAG fallback in Jenkinsfile

Jenkinsfile

@@ -13,20 +13,22 @@ pipeline {
     stages {
         stage('Build') {
             steps {
-                sh '''
+                script {
-                    docker build \
+                    def tag = params.TAG ?: 'latest'
-                        -t ${REGISTRY}:${TAG} \
+                    sh "docker build -t ${env.REGISTRY}:${tag} ."
-                        .
+                }
-                '''
             }
         }
 
         stage('Push') {
             steps {
-                sh '''
+                script {
-                    echo "${REGISTRY_CREDS_PSW}" | docker login atl.vultrcr.com -u "${REGISTRY_CREDS_USR}" --password-stdin
+                    def tag = params.TAG ?: 'latest'
-                    docker push ${REGISTRY}:${TAG}
+                    sh """
-                '''
+                        echo '${env.REGISTRY_CREDS_PSW}' | docker login atl.vultrcr.com -u '${env.REGISTRY_CREDS_USR}' --password-stdin
+                        docker push ${env.REGISTRY}:${tag}
+                    """
+                }
             }
         }
     }