fix overflow

main.c

@@ -72,7 +72,7 @@ static void avr_init()
 }
 
 void send_info(void){
-    char msg[4];
+    char msg[6];
     sprintf(msg, "%d", abzug_speed);
     mqtt_pub(&mqtt_client, "/Filamentanlage/05_Abzug/state/abzug/speed", msg, strlen(msg));