fix panic

[CiNcH83]

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x53ee54]

goroutine 865763 [running]:
main.readData(0x400012e000, {0x0, 0x0}, {0x40009d7be0, 0x1, 0x71dd07?})
        /home/Pi/repos/controlbox/frontend.go:95 +0x34
main.(*controlbox).OnLPCEvent(0x400012e000, {0x400015edb0, 0x28}, {0x829b38, 0x400009c240}, {0x0, 0x0}, {0x729af2, 0x1b})
        /home/Pi/repos/controlbox/controlbox.go:352 +0x22c
github.com/enbility/eebus-go/usecases/usecase.(*UseCaseBase).removeDeviceFromAvailableEntityScenarios(0x40000a8750, {0x829b38, 0x400009c240})
        /home/Pi/go/pkg/mod/github.com/enbility/eebus-go@v0.7.1-0.20250703122432-c2d97a2e53e0/usecases/usecase/usecase.go:231 +0xa4
github.com/enbility/eebus-go/usecases/usecase.(*UseCaseBase).deviceOrEntityRemoved(0x4000658f28?, {{0x400015edb0, 0x28}, 0x0, 0x2, {0x829b38, 0x400009c240}, {0x0, 0x0}, {0x0, ...}, ...})
        /home/Pi/go/pkg/mod/github.com/enbility/eebus-go@v0.7.1-0.20250703122432-c2d97a2e53e0/usecases/usecase/events.go:32 +0x44
github.com/enbility/eebus-go/usecases/usecase.(*UseCaseBase).HandleEvent(0x40000a8750, {{0x400015edb0, 0x28}, 0x0, 0x2, {0x829b38, 0x400009c240}, {0x0, 0x0}, {0x0, ...}, ...})
        /home/Pi/go/pkg/mod/github.com/enbility/eebus-go@v0.7.1-0.20250703122432-c2d97a2e53e0/usecases/usecase/events.go:13 +0x40
created by github.com/enbility/spine-go/spine.(*events).Publish in goroutine 865477
        /home/Pi/go/pkg/mod/github.com/enbility/spine-go@v0.7.1-0.20250822155603-08a28fe4480c/spine/events.go:100 +0x31c

[CiNcH83]

ping @andig