Add another flength() check before renaming bad QWK packets

To hopefully address:
!ERROR 2 (No such file or directory) renaming s:\sbbs\data\file/somenum.rep
 (-1 bytes) to s:\sbbs\data\file/somenum.rep.6777ed7c.bad

Clearly flength() is returning -1 (file doesn't exist) at this point, so
perhaps the call to fremove() just above updated a cached directory?

src/sbbs3/main.cpp

@@ -2975,7 +2975,7 @@ void event_thread(void* arg)
 					}
 					sbbs->lprintf(LOG_DEBUG, "Opened %s", lockfile.name);
 					if(!fexist(fname)) {
-						sbbs->lprintf(LOG_NOTICE, "%s already gone", fname);
+						sbbs->lprintf(LOG_DEBUG, "%s already gone", fname);
 						if(!fmutex_close(&lockfile))
 							sbbs->errormsg(WHERE, ERR_CLOSE, lockfile.name);
 						continue;
@@ -2995,14 +2995,16 @@ void event_thread(void* arg)
 						char badpkt[MAX_PATH+1];
 						SAFEPRINTF2(badpkt, "%s.%" PRIx64 ".bad", fname, (uint64_t)time(NULL));
 						sbbs->fremove(WHERE, badpkt);
-						if(rename(fname, badpkt) == 0)
-							sbbs->lprintf(LOG_NOTICE, "%s renamed to %s", fname, badpkt);
-						else
-							sbbs->lprintf(LOG_ERR, "!ERROR %d (%s) renaming %s (%ld bytes) to %s"
-								,errno, strerror(errno), fname, (long)flength(fname), badpkt);
-						SAFEPRINTF(badpkt, "%u.rep.*.bad", sbbs->useron.number);
-						SAFEPRINTF(str,"%sfile/", sbbs->cfg.data_dir);
-						sbbs->delfiles(str, badpkt, /* keep: */10);
+						if(flength(fname) > 0) {
+							if(rename(fname, badpkt) == 0)
+								sbbs->lprintf(LOG_NOTICE, "%s renamed to %s", fname, badpkt);
+							else
+								sbbs->lprintf(LOG_ERR, "!ERROR %d (%s) renaming %s (%ld bytes) to %s"
+									,errno, strerror(errno), fname, (long)flength(fname), badpkt);
+							SAFEPRINTF(badpkt, "%u.rep.*.bad", sbbs->useron.number);
+							SAFEPRINTF(str,"%sfile/", sbbs->cfg.data_dir);
+							sbbs->delfiles(str, badpkt, /* keep: */10);
+						}
 					}
 					if(!fmutex_close(&lockfile))
 						sbbs->errormsg(WHERE, ERR_CLOSE, lockfile.name);