fix standalone

CHANGELOG_LATEST.md

@@ -10,6 +10,7 @@ For more details go to [www.emsesp.org](https://www.emsesp.org/).
 
 - include HA "unit_of_meas", "stat_cla" and "dev_cla" attributes for Number sensors [#2149](https://github.com/emsesp/EMS-ESP32/issues/2149)
 - Bosch CS6800i AW - Silent Mode + Electrical Power Reduction (HP) [#2147](https://github.com/emsesp/EMS-ESP32/issues/2147)
+- system commands for showertimer and showeralert [#2168](https://github.com/emsesp/EMS-ESP32/discussions/2168)
 
 ## Fixed
 

lib_standalone/emsuart_standalone.h

@@ -36,6 +36,9 @@ class EMSuart {
     static void     restart();
     static void     send_poll(uint8_t data);
     static uint16_t transmit(uint8_t * buf, uint8_t len);
+    static uint8_t  last_tx_src() {
+        return 0;
+    }
 
   private:
     static char * hextoa(char * result, const uint8_t value);