On rule execution newly appeared error "sendCommand... on instance: null"

Hi everbody,

after weeks of working flawlessly my rule suddenly stops executing:

2016-04-23 10:17:19.978 [INFO ] [org.openhab.model.script.ALS ] - ALS rule OFF triggered
2016-04-23 10:17:20.695 [INFO ] [org.openhab.model.script.ALS ] - Turning off Nr11100_1
2016-04-23 10:17:20.704 [ERROR] [o.o.c.s.ScriptExecutionThread ] - Error during the execution of rule ‘Auf Knopfdruck alle Lampen aus’: Could not invoke method: org.openhab.model.script.actions.BusEvent.sendCommand(org.openhab.core.items.Item,java.lang.String) on instance: null
… and lots of gibberish after.

This is the rule in question which has been running without error for weeks (after lots of help here My problem with switching items all at once). Thanks to Rich again.

rule "Auf Knopfdruck alle Lampen aus"
when
Item ALS_Switch received command OFF
then
logInfo(“ALS”, “ALS rule OFF triggered”)
ALS.members.forEach[Switch|
logInfo(“ALS”, "Turning off " + Switch.name)
sendCommand(Switch, OFF)
Thread::sleep(2000)
]
logInfo(“ALS”, “End of ALS rule OFF reached”)
end

see