Use the sub-board internal as the default 'listname' if there is 'from' key

specified in the sub-board sections of the listgate.ini

This resolves the reported run-time error (due to misconfiguration):
10/13 09:59:23p !JavaScript d:\sbbs\mods\listgate.js line 86:
TypeError: from is undefined

exec/listgate.js

@@ -82,6 +82,9 @@ for(i in area) {
 	sub = area[i].sub;
 
 	from = area[i].from;
+	
+	if(!from)
+		from = sub;
 
 	if(from.indexOf('@')<0)	// automaticalliy append system's e-mail host/domain name
 		from+=('@'+system.inet_addr);