ARTEMIS-2582: EmbeddedActiveMQ.stop() should check for null

artemis-server/src/main/java/org/apache/activemq/artemis/core/server/embedded/EmbeddedActiveMQ.java

@@ -164,7 +164,9 @@ public class EmbeddedActiveMQ {
    }
 
    public EmbeddedActiveMQ stop() throws Exception {
-      activeMQServer.stop();
+      if (activeMQServer != null) {
+         activeMQServer.stop();
+      }
       return this;
    }
 }

artemis-server/src/test/java/org/apache/activemq/artemis/core/server/embedded/EmbeddedTest.java

@@ -0,0 +1,29 @@
+/**
+ * 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.activemq.artemis.core.server.embedded;
+
+import org.junit.Test;
+
+public class EmbeddedTest {
+
+   @Test
+   public void testNull() throws Exception {
+      EmbeddedActiveMQ embeddedActiveMQ = new EmbeddedActiveMQ();
+      embeddedActiveMQ.stop();
+   }
+}