handler with SendFile gets execution when no post handler found in jester 0.4
This is another weird situation @dom96. Code below terminates with a nil exception if a handler has the sendFile template if no 'post' handler is found.

_curl -d 'user=jondoe' http://localhost:5454/login_

```
import jester,htmlgen,os
settings:
    port = Port(5454)
    bindAddr = "127.0.0.1"
    staticDir = "tests/public"

routes:
  get "/":
    resp "Hello"
    
  get "/sendFile":
      sendFile(getCurrentDir() / "tests/public/root/test_file.txt")
  
  error Http404:
    resp "404"
    doAssert error.data.code != Http401
    resp error.data.code, "OK: " & $error.data.code
      
  error Http401:
    doAssert error.data.code == Http401
    resp error.data.code, "OK: " & $error.data.code
  
  error Exception:
    resp Http500, "Something bad happened: " & exception.msg  
```
![screenshot from 2018-07-26 17-10-46](https://user-images.githubusercontent.com/853846/43271235-4c9ea980-90f7-11e8-918a-af4779d879da.png)
