core version appears as an empty string

started container using the following command 
```bash
~ docker run --rm -it -p 8000:8000 stellar/quickstart --pubnet --enable core,horizon,rpc
```

core version appears to be empty string in horizon's root resource.  
```bash
➜  ~ curl localhost:8000 | jq '[.horizon_version,.core_version]'
[
  "horizon-v22.0.1-(built-from-source)",
  ""
]
```