openonuAdapterGo - HW-test: crash due to unresponsive rw-core

During test of SW-upgrade with real ONU-HW an unresponsive rw-core led to a crash of the adapter:

{"level":"error","ts":"2021-05-12T18:08:15.631Z","caller":"onuadaptercore/device_handler.go:2162","msg":"Failed to fetch parent device for OnuEvent","instanceId":"open-onu-voltha-adapter-openonu-7c44645675-4n8gk","pkg":"adaptercoreonu","op-name":"/voltha.VolthaService/EnableDevice","task-id":"46a0e300e49e4aba","task-name":"kafka-rpc-adopt_device","device-id":"306e9ffb-44ac-426f-b1db-4c5ad19fadb1","op-id":"42c071cca402e87c","parentID":"306e9ffb-44ac-426f-b1db-4c5ad19fadb1","err":"rpc error: code = DeadlineExceeded desc = context deadline exceeded","stacktrace":"github.com/opencord/voltha-lib-go/v4/pkg/log.clogger.Errorw\n\t/go/src/github.com/opencord/voltha-openonu-adapter-go/vendor/github.com/opencord/voltha-lib-go/v4/pkg/log/log.go:611\ngithub.com/opencord/voltha-openonu-adapter-go/internal/pkg/onuadaptercore.(*deviceHandler).sendOnuOperStateEvent\n\t/go/src/github.com/opencord/voltha-openonu-adapter-go/internal/pkg/onuadaptercore/device_handler.go:2162"}

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x90 pc=0xe086ef]

goroutine 3342388 [running]:
github.com/opencord/voltha-openonu-adapter-go/internal/pkg/onuadaptercore.(*deviceHandler).sendOnuOperStateEvent(0xc0000d86c0, 0x1434be0, 0xc00066a3c0, 0xc000000004, 0xc0004025a0, 0x24, 0x167e63f8ae7546f9)
/go/src/github.com/opencord/voltha-openonu-adapter-go/internal/pkg/onuadaptercore/device_handler.go:2165 +0x27f
created by github.com/opencord/voltha-openonu-adapter-go/internal/pkg/onuadaptercore.(*deviceHandler).processUniUnlockStateDoneEvent
/go/src/github.com/opencord/voltha-openonu-adapter-go/internal/pkg/onuadaptercore/device_handler.go:1873 +0x328
[adtran@node1-42 ~]$