Service crashed while receiving a beacon

I was using my local digipeater and the service crashed while I was out:

```
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x54abcb]

goroutine 11 [running]:
github.com/cceremuga/ionosphere/framework/marshaler.ToLogFormat(...)
/home/user/sdr/aprs/ionosphere/framework/marshaler/marshaler.go:35
github.com/cceremuga/ionosphere/handlers/stdout.Stdout.Handle({}, 0xc0001d3c80)
/home/user/sdr/aprs/ionosphere/handlers/stdout/stdout.go:42 +0x12b
github.com/cceremuga/ionosphere/services/packet.handle(0xc0001e7200?)
/home/user/sdr/aprs/ionosphere/services/packet/packet.go:47 +0x74
github.com/cceremuga/ionosphere/services/packet.Decode({0x5c9238?, 0xc000064ae0?})
/home/user/sdr/aprs/ionosphere/services/packet/packet.go:33 +0x15d
created by github.com/cceremuga/ionosphere/subprocesses/multimon.Start
/home/user/sdr/aprs/ionosphere/subprocesses/multimon/multimon.go:41 +0x28a
```

Start at framework/marshaler/marshaler.go:35, then follow the stack through handlers/stdout/stdout.go:42 and services/packet/packet.go:33-47. Reproduce receiving a beacon through the local digipeater and inspect the values passed into ToLogFormat. Done means the reported beacon path no longer crashes the service.

Written by the indexing model from the issue text.