OF-889 Avoid NPE when session partially shutdown

Where ioSession.getRemoteAddress() returns null, this can cause an NPE.

src/java/org/jivesoftware/openfire/nio/NIOConnection.java

@@ -165,6 +165,7 @@ public class NIOConnection implements Connection {
 
     public byte[] getAddress() throws UnknownHostException {
         final SocketAddress remoteAddress = ioSession.getRemoteAddress();
+        if (remoteAddress == null) throw new UnknownHostException();
         final InetSocketAddress socketAddress = (InetSocketAddress) remoteAddress;
         final InetAddress address = socketAddress.getAddress();
         return address.getAddress();
@@ -172,6 +173,7 @@ public class NIOConnection implements Connection {
 
     public String getHostAddress() throws UnknownHostException {
         final SocketAddress remoteAddress = ioSession.getRemoteAddress();
+        if (remoteAddress == null) throw new UnknownHostException();
         final InetSocketAddress socketAddress = (InetSocketAddress) remoteAddress;
         final InetAddress inetAddress = socketAddress.getAddress();
         return inetAddress.getHostAddress();
@@ -179,6 +181,7 @@ public class NIOConnection implements Connection {
 
     public String getHostName() throws UnknownHostException {
         final SocketAddress remoteAddress = ioSession.getRemoteAddress();
+        if (remoteAddress == null) throw new UnknownHostException();
         final InetSocketAddress socketAddress = (InetSocketAddress) remoteAddress;
         final InetAddress inetAddress = socketAddress.getAddress();
         return inetAddress.getHostName();