Fixes NULL pointer dereference (CVE-2006-6719)

================================================================================
--- src/ftp-basic.c
+++ src/ftp-basic.c
@@ -1039,7 +1039,9 @@
      first word of the server response)?  */
   request = strtok (NULL, " ");
 
-  if (!strcasecmp (request, "VMS"))
+  if (request == NULL)
+    *server_type = ST_OTHER;
+  else if (!strcasecmp (request, "VMS"))
     *server_type = ST_VMS;
   else if (!strcasecmp (request, "UNIX"))
     *server_type = ST_UNIX;