fix compilation error #74

Job	Run time
debug	1s
Build nodemcu-32s	1m 51s
Build espressif_esp-wrover-kit	2m 2s
Build espressif_esp-wrover-kit_latest	2m 2s
Build adafruit_huzzah32_dev	2m 2s
Build adafruit_huzzah32	1m 57s
Build adafruit_featheresp32	2m 0s
Build openevse_wifi_v1	2m 5s
Build olimex_esp32-gateway-old	2m 5s
Build olimex_esp32-gateway-e	1m 52s
Build olimex_esp32-gateway-f	1m 51s
Build olimex_esp32-gateway-e_dev	2m 5s
Build olimex_esp32-gateway-f_dev	2m 26s
Build olimex_esp32-poe-iso	2m 5s
Build heltec_esp32-wifi-lora-v2	2m 8s
Build wt32-eth01	1m 55s
Build esp32-c3-devkitc-02	2m 13s
Build elecrow_esp32_hmi	2m 8s
Build elecrow_esp32_hmi_dev	2m 18s
Build openevse_wifi_tft_v1	2m 23s
Build openevse_wifi_tft_v1_dev	2m 23s
Upload release assets	37s
	42m 29s

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