Open olt adapter is crashing during delete device

Open olt adapter is crashing when a delete device request is received parallelly when processing flows.

 

{"level":"warn","ts":"2023-11-21T06:01:13.524Z","caller":"core/device_handler.go:517","msg":"error-during-enable-indications","instanceId":"vstack1-adapter-openolt-5bf7945b9c-nfdjm","err":"rpc error: code = Canceled desc = grpc: the client connection is closing","device-id":"5eeee54b-49e3-3a9c-8c51-4882e1c1f7c2","stacktrace":"github.com/opencord/voltha-openolt-adapter/internal/pkg/core.(*DeviceHandler).readIndications\n\t/go/src/internal/pkg/core/device_handler.go:517\ngithub.com/opencord/voltha-openolt-adapter/internal/pkg/core.startHeartbeatCheck.func2\n\t/go/src/internal/pkg/core/device_handler.go:2466"}

{"level":"warn","ts":"2023-11-21T06:01:49.975Z","caller":"core/device_handler.go:2438","msg":"heartbeat-failed","instanceId":"vstack1-adapter-openolt-5bf7945b9c-nfdjm","device-id":"b7cf9d52-14e0-394e-b19d-c57fd1d6a46f","stacktrace":"github.com/opencord/voltha-openolt-adapter/internal/pkg/core.startHeartbeatCheck\n\t/go/src/internal/pkg/core/device_handler.go:2438"} {"level":"warn","ts":"2023-11-21T06:02:06.975Z","caller":"core/device_handler.go:2438","msg":"heartbeat-failed","instanceId":"vstack1-adapter-openolt-5bf7945b9c-nfdjm","device-id":"b7cf9d52-14e0-394e-b19d-c57fd1d6a46f","stacktrace":"github.com/opencord/voltha-openolt-adapter/internal/pkg/core.startHeartbeatCheck\n\t/go/src/internal/pkg/core/device_handler.go:2438"} {"level":"warn","ts":"2023-11-21T06:02:20.977Z","caller":"core/device_handler.go:2502","msg":"update-state-unreachable","instanceId":"vstack1-adapter-openolt-5bf7945b9c-nfdjm","device-id":"b7cf9d52-14e0-394e-b19d-c57fd1d6a46f","connect-status":"REACHABLE","admin-state":"ENABLED","oper-status":"ACTIVE","stacktrace":"github.com/opencord/voltha-openolt-adapter/internal/pkg/core.(*DeviceHandler).updateStateUnreachable\n\t/go/src/internal/pkg/core/device_handler.go:2502\ngithub.com/opencord/voltha-openolt-adapter/internal/pkg/core.startHeartbeatCheck.func1\n\t/go/src/internal/pkg/core/device_handler.go:2441"} {"level":"warn","ts":"2023-11-21T06:02:20.982Z","caller":"core/device_handler.go:517","msg":"error-during-enable-indications","instanceId":"vstack1-adapter-openolt-5bf7945b9c-nfdjm","err":"rpc error: code = Canceled desc = grpc: the client connection is closing","device-id":"b7cf9d52-14e0-394e-b19d-c57fd1d6a46f","stacktrace":"github.com/opencord/voltha-openolt-adapter/internal/pkg/core.(*DeviceHandler).readIndications\n\t/go/src/internal/pkg/core/device_handler.go:517\ngithub.com/opencord/voltha-openolt-adapter/internal/pkg/core.startHeartbeatCheck.func2\n\t/go/src/internal/pkg/core/device_handler.go:2466"}

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x68 pc=0xeb7197]
 
goroutine 6466033 [running]:
github.com/opencord/voltha-openolt-adapter/internal/pkg/core.(*OpenOltFlowMgr).StopAllFlowHandlerRoutines(0x0, 0x12fac80, 0xc231d47620, 0xc367ac81a0)
/go/src/internal/pkg/core/openolt_flowmgr.go:2308 +0x37
created by github.com/opencord/voltha-openolt-adapter/internal/pkg/core.(*DeviceHandler).DeleteDevice
/go/src/internal/pkg/core/device_handler.go:2168 +0x256