internal/trace: nil deref

[dvyukov]

cmd/trace crashes on the following input:

"gotrace\x00T00\x020"

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x463466]

goroutine 1 [running]:
internal/trace.postProcessTrace(0xc82009c800, 0x2f, 0x40, 0x0, 0x0)
        src/internal/trace/parser.go:534 +0x3936
internal/trace.Parse(0x7ff4a485c1c0, 0xc8200144e0, 0x0, 0x0, 0x0, 0x0, 0x0)
        src/internal/trace/parser.go:73 +0x3d9
cmd/trace/fuzz.Fuzz(0x7ff4a4658000, 0x1df, 0x200000, 0x3)
        src/cmd/trace/fuzz/main.go:9 +0x143
github.com/dvyukov/go-fuzz/go-fuzz-dep.Main(0x59f460)
        /home/dvyukov/src/gopath/src/github.com/dvyukov/go-fuzz/go-fuzz-dep/main.go:44 +0x14c
main.main()
        src/go-fuzz-main/main.go:10 +0x23

go version devel +9b04852 Sat Jul 11 00:08:50 2015 +0000 linux/amd64

[gopherbot]

CL https://golang.org/cl/12378 mentions this issue.