Update powerwall.sh

powerwall.sh

@@ -245,7 +245,7 @@ CHECKTEMP_SERVICE(){
 				fi
 				if [ "${SENSORS_CHECK}" != "" ]; then
 					for SENSOR in "${SENSORS_CHECK[@]}"; do
-						[ ! "${last_temp[${SENSOR}]}" ] && last_temp[${SENSOR}]=0
+						[ "${last_temp[${SENSOR}]}" == "" ] && last_temp[${SENSOR}]=0
 						if [ "${PW_THRESHOLDS[${SENSORa}]}" != "" ]; then
 							echo ${PW_THRESHOLDS[${SENSORa}]} | cut -d',' -f 1 | read temp_warn
 							echo ${PW_THRESHOLDS[${SENSORa}]} | cut -d',' -f 2 | read temp_crit