Don't allow active_clients counter to go negative.

src/sbbs3/mailsrvr.c

@@ -1186,6 +1186,7 @@ static void pop3_thread(void* arg)
 	smb_freemsgmem(&msg);
 	smb_close(&smb);
 
+	if(active_clients)
 		active_clients--, update_clients();
 	client_off(socket);
 
@@ -1637,6 +1638,7 @@ static void smtp_thread(void* arg)
 			lprintf("%04d !SMTP REFUSED SESSION from blacklisted server"
 				,socket);
 			thread_down();
+			if(active_clients)
 				active_clients--, update_clients();
 			return;
 		}
@@ -1654,6 +1656,7 @@ static void smtp_thread(void* arg)
 		sockprintf(socket,sys_error);
 		mail_close_socket(socket);
 		thread_down();
+		if(active_clients)
 			active_clients--, update_clients();
 		return;
 	}
@@ -2767,6 +2770,7 @@ static void smtp_thread(void* arg)
 
 	status(STATUS_WFC);
 
+	if(active_clients)
 		active_clients--, update_clients();
 	client_off(socket);
 
@@ -3436,8 +3440,7 @@ void DLLCALL mail_server(void* arg)
 
 		lprintf("Maximum inactivity: %u seconds",startup->max_inactivity);
 
-		active_clients=0;
-		update_clients();
+		active_clients=0,update_clients();
 
 		/* open a socket and wait for a client */
 
@@ -3719,7 +3722,7 @@ void DLLCALL mail_server(void* arg)
 			start=time(NULL);
 			while(active_clients) {
 				if(time(NULL)-start>TIMEOUT_THREAD_WAIT) {
-					lprintf("!TIMEOUT waiting for %u active clients ",active_clients);
+					lprintf("!TIMEOUT waiting for %d active clients ",active_clients);
 					break;
 				}
 				mswait(100);