5910 libnisdb won't build with modern GCC

@@ -18,16 +18,15 @@
  * information: Portions Copyright [yyyy] [name of copyright owner]
  *
  * CDDL HEADER END
  */
 /*
+ * Copyright 2015 Gary Mills
  * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
-#pragma ident   "%Z%%M% %I%     %E% SMI"
-
 /*
  * DESCRIPTION: Contains the map update thread and related code.
  */
 
 #include <unistd.h>

@@ -356,10 +355,12 @@
 
         /* Free up duplicate copy of the map_ctrl */
         free_map_ctrl(map);
 
         thr_exit(ret);
+
+        return (NULL);
 }
 
 /*
  * FUNCTION :   is_special_key()
  *