Error when used Array of Handlers as last position on router

Using of arrays on Handlers work on the beginning and in the middle, but when array is on last position of router definition, it is not propagated and it throws this error:

```
error: Internal server error: handler.call is not a function handler.call is not a function
```
This is thrown from [this line](https://github.com/spatools/express-async-router/blob/master/index.ts#L179).

