Fix observed crash when writing to hungup.log, node.aux was a large number

(greater than the number of configured externals) - I'm not sure why I was
using the value from the node.dab here, but it wasn't necessary so using local
variable now instead.

src/sbbs3/xtrn_sec.cpp

@@ -8,7 +8,7 @@
  * @format.tab-size 4		(Plain Text/Source Code File Header)			*
  * @format.use-tabs true	(see http://www.synchro.net/ptsc_hdr.html)		*
  *																			*
- * Copyright 2011 Rob Swindell - http://www.synchro.net/copyright.html		*
+ * Copyright 2012 Rob Swindell - http://www.synchro.net/copyright.html		*
  *																			*
  * This program is free software; you can redistribute it and/or			*
  * modify it under the terms of the GNU General Public License				*
@@ -1760,10 +1760,8 @@ bool sbbs_t::exec_xtrn(uint xtrnnum)
 			errormsg(WHERE,ERR_OPEN,str,O_WRONLY|O_CREAT|O_APPEND);
 			return(false); 
 		}
-		getnodedat(cfg.node_num,&thisnode,0);
 		now=time(NULL);
-		sprintf(str,hungupstr,useron.alias,thisnode.aux ? cfg.xtrn[thisnode.aux-1]->name : "External Program"
-			,timestr(now));
+		SAFEPRINTF3(str,hungupstr,useron.alias,cfg.xtrn[xtrnnum]->name,timestr(now));
 		write(file,str,strlen(str));
 		close(file); 
 	}