Random segmentation fault when using orc and threads more than 1
This minimal code should reproduce the issue.
```nim
# hello.nim
import options, asyncdispatch, logging

import httpbeast

proc onRequest(req: Request): Future[void] =
  if req.httpMethod == some(HttpGet):
    case req.path.get()
    of "/":
      req.send("Hello World")
    else:
      req.send(Http404)

if logging.getHandlers().len == 0:
  addHandler(logging.newConsoleLogger())
  setLogFilter(when defined(release): lvlInfo else: lvlDebug)

run(onRequest, httpbeast.initSettings(numThreads=2))
```
```bash
nim c -r --gc:orc -d:releae --threads:on hello.nim
```
- Nim version `1.6.8`
- httpbeast version `0.4.1`
- Run inside docker image `nimlang/nim` (also tried with WSL2 and GCP debian instance)

When running and killing the binary multiple times, the program sometimes runs but most of the times it gives this error:
```bash
root@4dfa057c787d:~# ./hello
Starting 2 threads
Listening on port 8080
Traceback (most recent call last)
/root/.nimble/pkgs/httpbeast-0.4.1/httpbeast.nim(83) eventLoop
/nim/lib/system/orc.nim(46) nimIncRefCyclic
SIGSEGV: Illegal storage access. (Attempt to read from nil?)
Segmentation fault
```
I initially found the issue when using Jester. After some searching I found that I can solve the issue by commenting this block of code. Other workaround that I did was modifying `Settings.loggers` to `ref seq[Logger]`, which also removes the random segfault.
https://github.com/dom96/httpbeast/blob/7de559e6eab97763bae16b8a973373e9fe691574/src/httpbeast.nim#L336-L339