Merge pull request #2040 from lebron374/npe_fix_v1

[ISSUE #1798] Fix MessageExt#getBornHostString NPE

common/src/main/java/org/apache/rocketmq/common/message/MessageExt.java

@@ -142,18 +142,20 @@ public class MessageExt extends Message {
     }
 
     public String getBornHostString() {
-        if (this.bornHost != null) {
-            InetSocketAddress inetSocketAddress = (InetSocketAddress) this.bornHost;
-            return inetSocketAddress.getAddress().getHostAddress();
+        if (null != this.bornHost) {
+            InetAddress inetAddress = ((InetSocketAddress) this.bornHost).getAddress();
+
+            return null != inetAddress ? inetAddress.getHostAddress() : null;
         }
 
         return null;
     }
 
     public String getBornHostNameString() {
-        if (this.bornHost != null) {
-            InetSocketAddress inetSocketAddress = (InetSocketAddress) this.bornHost;
-            return inetSocketAddress.getAddress().getHostName();
+        if (null != this.bornHost) {
+            InetAddress inetAddress = ((InetSocketAddress) this.bornHost).getAddress();
+
+            return null != inetAddress ? inetAddress.getHostName() : null;
         }
 
         return null;