WW-4419 Fixes NPE when performing async request

plugins/sitemesh/src/main/java/org/apache/struts2/sitemesh/StrutsSiteMeshFactory.java

@@ -1,14 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
 package org.apache.struts2.sitemesh;
 
 import com.opensymphony.module.sitemesh.Config;
 import com.opensymphony.module.sitemesh.factory.DefaultFactory;
+import com.opensymphony.xwork2.ActionContext;
+import com.opensymphony.xwork2.util.logging.Logger;
+import com.opensymphony.xwork2.util.logging.LoggerFactory;
 import org.apache.commons.lang3.ObjectUtils;
 import org.apache.struts2.ServletActionContext;
 import org.apache.struts2.StrutsStatics;
 
-
 public class StrutsSiteMeshFactory extends DefaultFactory {
 
+    private static final Logger LOG = LoggerFactory.getLogger(StrutsSiteMeshFactory.class);
+
     public StrutsSiteMeshFactory(Config config) {
         super(config);
     }
@@ -22,7 +44,14 @@ public boolean shouldParsePage(String contentType) {
     }
 
     private boolean isInsideActionTag() {
+        if(ActionContext.getContext() == null) {
+            if (LOG.isTraceEnabled()) {
+                LOG.trace("ActionContext is null! Not a user request?");
+            }
+            return false;
+        }
         Object attribute = ServletActionContext.getRequest().getAttribute(StrutsStatics.STRUTS_ACTION_TAG_INVOCATION);
         return (Boolean) ObjectUtils.defaultIfNull(attribute, Boolean.FALSE);
     }
+
 }