Don't save draft messages upon disconnect for Guest or "no one" (user #0)

Fix issue #508

src/sbbs3/writemsg.cpp

@@ -604,7 +604,7 @@ bool sbbs_t::writemsg(const char *fname, const char *top, char *subj, long mode,
 		rioctl(IOSM|PAUSE|ABORT); 
 
 		checkline();
-		if(!online && flength(msgtmp) > 0)	 { // save draft message due to disconnection
+		if(!online && (flength(msgtmp) > 0) && (useron.number > 0) && !(useron.rest & FLAG('G'))) { // save draft message due to disconnection
 			if(mv(msgtmp, draft, /* copy: */true) == 0) {
 				user_set_property(&cfg, useron.number, draft_desc, "subject", subj);
 				user_set_time_property(&cfg, useron.number, draft_desc, "created", time(NULL));