THRIFT-493. java: Stopping TNonblockingServer when it hasn't been starting results in an exception

Check if the server is null before trying to stop.



git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@773632 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/java/src/org/apache/thrift/server/TNonblockingServer.java b/lib/java/src/org/apache/thrift/server/TNonblockingServer.java
index 95d81e2..6d040a7 100644
--- a/lib/java/src/org/apache/thrift/server/TNonblockingServer.java
+++ b/lib/java/src/org/apache/thrift/server/TNonblockingServer.java
@@ -247,7 +247,9 @@
    */
   public void stop() {
     stopped_ = true;
-    selectThread_.wakeupSelector();
+    if (selectThread_ != null) {
+      selectThread_.wakeupSelector();
+    }
   }
 
   /**