panic: assignment to entry in nil map

goroutine 1 [running]:
github.com/google/syzkaller/pkg/signal.Serial.Deserialize(0xc000369500, 0x0, 0x0, 0xc000324a00, 0x690, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/pkg/signal/signal.go:91 +0xa0
main.(*Fuzzer).addInputFromAnotherFuzzer(0xc0000b0d00, 0xc000092ba0, 0x28, 0xc000448140, 0x126, 0x126, 0xc000369500, 0x690, 0x690, 0xc000324a00, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/syz-fuzzer/fuzzer.go:439 +0x103
main.(*Fuzzer).poll(0xc0000b0d00, 0x99e200, 0x0, 0xc00033be78)
	/syzkaller/gopath/src/github.com/google/syzkaller/syz-fuzzer/fuzzer.go:412 +0x427
main.main()
	/syzkaller/gopath/src/github.com/google/syzkaller/syz-fuzzer/fuzzer.go:267 +0x11d6