Fix nil pointer dereference

[fasmat]

Motivation

Latest release causes a nil pointer dereference error for some users:

2023-08-21T19:48:11.170+0800	INFO	grpc.Smesher	GRPC SmesherService.PostSetupStatus	{"module": "grpc"}
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x1 addr=0x0 pc=0x7ff6c6731597]

goroutine 27356 [running]:
github.com/spacemeshos/go-spacemesh/api/grpcserver.statusToPbStatus(...)
	D:/a/go-spacemesh/go-spacemesh/api/grpcserver/smesher_service.go:261
github.com/spacemeshos/go-spacemesh/api/grpcserver.SmesherService.PostSetupStatus({{0x7ff6c75ea7e8, 0xc0148d8510}, {0x7ff6c75dff30, 0xc008a7c800}, {0x7ff6c75e7370, 0xc000626540}, 0x3b9aca00, {{0xc0006b3008, 0x14}, 0x1c, ...}}, ...)
	D:/a/go-spacemesh/go-spacemesh/api/grpcserver/smesher_service.go:180 +0x97
github.com/spacemeshos/api/release/go/spacemesh/v1._SmesherService_PostSetupStatus_Handler.func1({0x7ff6c75def38, 0xc001ae2ea0}, {0x7ff6c6f7d200?, 0xc001ae2d50})
	C:/Users/runneradmin/go/pkg/mod/github.com/spacemeshos/api/release/go@v1.19.0/spacemesh/v1/smesher.pb.go:673 +0x78
github.com/grpc-ecosystem/go-grpc-middleware/logging/zap.UnaryServerInterceptor.func1({0x7ff6c75def38, 0xc001ae2db0}, {0x7ff6c6f7d200, 0xc001ae2d50}, 0xc000514ee0, 0xc003ad7800)
	C:/Users/runneradmin/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.4.0/logging/zap/server_interceptors.go:31 +0x115
google.golang.org/grpc.getChainUnaryHandler.func1({0x7ff6c75def38, 0xc001ae2db0}, {0x7ff6c6f7d200, 0xc001ae2d50})
	C:/Users/runneradmin/go/pkg/mod/google.golang.org/grpc@v1.57.0/server.go:1179 +0xb9
github.com/grpc-ecosystem/go-grpc-middleware/tags.UnaryServerInterceptor.func1({0x7ff6c75def38?, 0xc001ae2cf0?}, {0x7ff6c6f7d200, 0xc001ae2d50}, 0xc000514ee0, 0xc014a5d3c0)
	C:/Users/runneradmin/go/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.4.0/tags/interceptors.go:23 +0xa6
google.golang.org/grpc.chainUnaryInterceptors.func1({0x7ff6c75def38, 0xc001ae2cf0}, {0x7ff6c6f7d200, 0xc001ae2d50}, 0xc006235a58?, 0x7ff6c6ecd660?)
	C:/Users/runneradmin/go/pkg/mod/google.golang.org/grpc@v1.57.0/server.go:1170 +0x8f
github.com/spacemeshos/api/release/go/spacemesh/v1._SmesherService_PostSetupStatus_Handler({0x7ff6c70c1f00?, 0xc000278a20}, {0x7ff6c75def38, 0xc001ae2cf0}, 0xc0065aae70, 0xc005512820)
	C:/Users/runneradmin/go/pkg/mod/github.com/spacemeshos/api/release/go@v1.19.0/spacemesh/v1/smesher.pb.gopanic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x1 addr=0x0 pc=0x7ff6c6731597]

Changes

• ensure ProviderID is initialized before dereferencing

Test Plan

• new tests were added that failed the same way as reported by affected users and pass with the change.

TODO

• Explain motivation or link existing issue(s)
• Test changes and document test plan
• Update documentation as needed

DevOps Notes

• This PR does not require configuration changes (e.g., environment variables, GitHub secrets, VM resources)
• This PR does not affect public APIs
• This PR does not rely on a new version of external services (PoET, elasticsearch, etc.)
• This PR does not make changes to log messages (which monitoring infrastructure may rely on)