fix openhab error: Rule ‘[rulename]’: An error occurred during the script execution: index=0, size=0

My goal is to execute an python-script when the Battery-charge has reached 70%

My rule was not executed, the error as shown above is seen in the log.
My faulty script:

rule "BYD 70"

when
     Item KOSTALPLENTICOREPlus70WithBattery_BatteryCharge received update



then
	var BYDBat = (KOSTALPLENTICOREPlus70WithBattery_BatteryCharge.state as Number).floatValue

	if ((KOSTALPLENTICOREPlus70WithBattery_BatteryCharge.state as Number).floatValue = 70.0) {


	sendTelegram("bot1",
            "BYD hat > 70  % Ladung " + BYDBat)
	executeCommandLine("python3 /etc/openhab2/scripts/BYDI.py")
	logDebug("logtest", "BYDBat = " + BYDBat)
        logDebug("logtest", "state = " + KOSTALPLENTICOREPlus70WithBattery_BatteryCharge.state)
}

end

Reason of the error: the if-statement is misleading, to check if the value is equal it needs two “==”:

	if ((KOSTALPLENTICOREPlus70WithBattery_BatteryCharge.state as Number).floatValue == 70.0) {

working-code:

rule "BYD 70"

when
     Item KOSTALPLENTICOREPlus70WithBattery_BatteryCharge received update



then
	var BYDBat = (KOSTALPLENTICOREPlus70WithBattery_BatteryCharge.state as Number).floatValue

	if ((KOSTALPLENTICOREPlus70WithBattery_BatteryCharge.state as Number).floatValue == 70.0) {


	sendTelegram("bot1",
            "BYD hat > 70  % Ladung " + BYDBat)
	executeCommandLine("python3 /etc/openhab2/scripts/BYDI.py")
	logDebug("logtest", "BYDBat = " + BYDBat)
        logDebug("logtest", "state = " + KOSTALPLENTICOREPlus70WithBattery_BatteryCharge.state)
}

end

to debug BYDBat/KOSTALPLENTICOREPlus70WithBattery_BatteryCharge.state debugging needs to be enabled like shown at: https://www.cipv6.de/worp/index.php/2019/10/23/how-do-i-debug-tradfri-on-openhab/

openhab> log:get org.eclipse.smarthome.model.script
DEBUG
openhab> log:set Info org.eclipse.smarthome.model.script
openhab> log:get org.eclipse.smarthome.model.script
INFO