Treat every login failure with no password available as unique

When loginFailure() is called with NULL for the password argument, that indicates there was no password available (e.g. an aborted login attempt) - treat each of these as a unique (not duplicate) failed-login attempt. This'll trigger ban/filter thresholds sooner for clients that hammer servers and disconnect mid-login.

src/sbbs3/userdat.c

@@ -3253,7 +3253,7 @@ ulong loginFailure(link_list_t* list, const union xp_sockaddr* addr, const char*
 	if((node=login_attempted(list, addr)) != NULL) {
 		attempt=node->data;
 		/* Don't count consecutive duplicate attempts (same name and password): */
-		if((user!=NULL && strcmp(attempt->user,user)==0) && (pass==NULL || strcmp(attempt->pass,pass)==0))
+		if((user!=NULL && strcmp(attempt->user,user)==0) && (pass!=NULL && strcmp(attempt->pass,pass)==0))
 			attempt->dupes++;
 	}
 	SAFECOPY(attempt->prot,prot);