lightwalletd crashed hushd is running #60

Lightwalletd crashed while hush3 is running:

panic: interface conversion: interface {} is nil, not string


goroutine 46586 [running]:
git.hush.is/hush/lightwalletd/common.GetCoinsupply()
        /home/hush/lightwalletd/common/common.go:344 +0x505
git.hush.is/hush/lightwalletd/frontend.(*lwdStreamer).GetCoinsupply(0xc001212c40, {0x93cc9b?, 0xc001ab3080?}, 0xc001ab31d0?)
        /home/hush/lightwalletd/frontend/service.go:240 +0x36
git.hush.is/hush/lightwalletd/walletrpc._CompactTxStreamer_GetCoinsupply_Handler.func1({0xe0f778, 0xc001ab2f90}, {0xb3a8e0?, 0xc001ab2fc0})
        /home/hush/lightwalletd/walletrpc/service_grpc.pb.go:833 +0x78
github.com/grpc-ecosystem/go-grpc-prometheus.(*ServerMetrics).UnaryServerInterceptor.func1({0xe0f778, 0xc001ab2f90}, {0xb3a8e0, 0xc001ab2fc0}, 0xc000359748?, 0xc000742e88)
        /home/hush/lightwalletd/vendor/github.com/grpc-ecosystem/go-grpc-prometheus/server_metrics.go:107 +0x87
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1({0xe0f778?, 0xc001ab2f90?}, {0xb3a8e0?, 0xc001ab2fc0?})
        /home/hush/lightwalletd/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go:25 +0x3a
git.hush.is/hush/lightwalletd/common/logging.LogInterceptor({0xe0f778, 0xc001ab2f90}, {0xb3a8e0, 0xc001ab2fc0}, 0xc000312d00, 0xc000312d20)
        /home/hush/lightwalletd/common/logging/logging.go:36 +0xa4
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1({0xe0f778?, 0xc001ab2f90?}, {0xb3a8e0?, 0xc001ab2fc0?})
        /home/hush/lightwalletd/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go:25 +0x3a
github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1({0xe0f778, 0xc001ab2f90}, {0xb3a8e0, 0xc001ab2fc0}, 0xc0000a2a20?, 0xafdc40?)
        /home/hush/lightwalletd/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go:34 +0xbe
git.hush.is/hush/lightwalletd/walletrpc._CompactTxStreamer_GetCoinsupply_Handler({0xb9ebc0?, 0xc001212c40}, {0xe0f778, 0xc001ab2f90}, 0xc00026a540, 0xc00029c870)
        /home/hush/lightwalletd/walletrpc/service_grpc.pb.go:835 +0x138
google.golang.org/grpc.(*Server).processUnaryRPC(0xc0002061e0, {0xe13998, 0xc0003729c0}, 0xc0018099e0, 0xc00029c5a0, 0x127a2d8, 0x0)
        /home/hush/lightwalletd/vendor/google.golang.org/grpc/server.go:1340 +0xd23
google.golang.org/grpc.(*Server).handleStream(0xc0002061e0, {0xe13998, 0xc0003729c0}, 0xc0018099e0, 0x0)
        /home/hush/lightwalletd/vendor/google.golang.org/grpc/server.go:1713 +0xa2f
google.golang.org/grpc.(*Server).serveStreams.func1.2()
        /home/hush/lightwalletd/vendor/google.golang.org/grpc/server.go:965 +0x98
created by google.golang.org/grpc.(*Server).serveStreams.func1
        /home/hush/lightwalletd/vendor/google.golang.org/grpc/server.go:963 +0x28a

Lightwalletd crashed while hush3 is running: ``` panic: interface conversion: interface {} is nil, not string goroutine 46586 [running]: git.hush.is/hush/lightwalletd/common.GetCoinsupply() /home/hush/lightwalletd/common/common.go:344 +0x505 git.hush.is/hush/lightwalletd/frontend.(*lwdStreamer).GetCoinsupply(0xc001212c40, {0x93cc9b?, 0xc001ab3080?}, 0xc001ab31d0?) /home/hush/lightwalletd/frontend/service.go:240 +0x36 git.hush.is/hush/lightwalletd/walletrpc._CompactTxStreamer_GetCoinsupply_Handler.func1({0xe0f778, 0xc001ab2f90}, {0xb3a8e0?, 0xc001ab2fc0}) /home/hush/lightwalletd/walletrpc/service_grpc.pb.go:833 +0x78 github.com/grpc-ecosystem/go-grpc-prometheus.(*ServerMetrics).UnaryServerInterceptor.func1({0xe0f778, 0xc001ab2f90}, {0xb3a8e0, 0xc001ab2fc0}, 0xc000359748?, 0xc000742e88) /home/hush/lightwalletd/vendor/github.com/grpc-ecosystem/go-grpc-prometheus/server_metrics.go:107 +0x87 github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1({0xe0f778?, 0xc001ab2f90?}, {0xb3a8e0?, 0xc001ab2fc0?}) /home/hush/lightwalletd/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go:25 +0x3a git.hush.is/hush/lightwalletd/common/logging.LogInterceptor({0xe0f778, 0xc001ab2f90}, {0xb3a8e0, 0xc001ab2fc0}, 0xc000312d00, 0xc000312d20) /home/hush/lightwalletd/common/logging/logging.go:36 +0xa4 github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1.1.1({0xe0f778?, 0xc001ab2f90?}, {0xb3a8e0?, 0xc001ab2fc0?}) /home/hush/lightwalletd/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go:25 +0x3a github.com/grpc-ecosystem/go-grpc-middleware.ChainUnaryServer.func1({0xe0f778, 0xc001ab2f90}, {0xb3a8e0, 0xc001ab2fc0}, 0xc0000a2a20?, 0xafdc40?) /home/hush/lightwalletd/vendor/github.com/grpc-ecosystem/go-grpc-middleware/chain.go:34 +0xbe git.hush.is/hush/lightwalletd/walletrpc._CompactTxStreamer_GetCoinsupply_Handler({0xb9ebc0?, 0xc001212c40}, {0xe0f778, 0xc001ab2f90}, 0xc00026a540, 0xc00029c870) /home/hush/lightwalletd/walletrpc/service_grpc.pb.go:835 +0x138 google.golang.org/grpc.(*Server).processUnaryRPC(0xc0002061e0, {0xe13998, 0xc0003729c0}, 0xc0018099e0, 0xc00029c5a0, 0x127a2d8, 0x0) /home/hush/lightwalletd/vendor/google.golang.org/grpc/server.go:1340 +0xd23 google.golang.org/grpc.(*Server).handleStream(0xc0002061e0, {0xe13998, 0xc0003729c0}, 0xc0018099e0, 0x0) /home/hush/lightwalletd/vendor/google.golang.org/grpc/server.go:1713 +0xa2f google.golang.org/grpc.(*Server).serveStreams.func1.2() /home/hush/lightwalletd/vendor/google.golang.org/grpc/server.go:965 +0x98 created by google.golang.org/grpc.(*Server).serveStreams.func1 /home/hush/lightwalletd/vendor/google.golang.org/grpc/server.go:963 +0x28a ```

It is complaining about this line :

https://git.hush.is/hush/lightwalletd/src/branch/master/common/common.go#L344

so my guess is that the coinsupply RPC returned some funky data or maybe timed out and lightwalletd code did not like that. The lightwalletd code needs to be improved to handle this gracefully.