Cannot read property 'slice' of undefined

```
OliverSalzburg@Oliver-PC MINGW64 ~/Projects/absync (dev)
$ karma init karma.conf.js
> readline.js:525
this.line = this.line.slice(this.cursor);
^

TypeError: Cannot read property 'slice' of undefined
at Interface._deleteLineLeft (readline.js:525:24)
at suggestNextOption (C:\Users\Oliver\Projects\absync\node_modules\karma\lib\init\state_machine.js:43:9)
at nextQuestion (C:\Users\Oliver\Projects\absync\node_modules\karma\lib\init\state_machine.js:119:12)
at process (C:\Users\Oliver\Projects\absync\node_modules\karma\lib\init\state_machine.js:135:10)
at Object.exports.init (C:\Users\Oliver\Projects\absync\node_modules\karma\lib\init.js:247:6)
at Object.exports.run (C:\Users\Oliver\Projects\absync\node_modules\karma\lib\cli.js:237:25)
at requireCliAndRun (C:\Users\Oliver\AppData\Roaming\npm\node_modules\karma-cli\bin\karma:44:16)
at C:\Users\Oliver\AppData\Roaming\npm\node_modules\karma-cli\bin\karma:54:12
at C:\Users\Oliver\AppData\Roaming\npm\node_modules\karma-cli\node_modules\resolve\lib\async.js:44:21
at ondir (C:\Users\Oliver\AppData\Roaming\npm\node_modules\karma-cli\node_modules\resolve\lib\async.js:187:31)
at C:\Users\Oliver\AppData\Roaming\npm\node_modules\karma-cli\node_modules\resolve\lib\async.js:153:39
at onex (C:\Users\Oliver\AppData\Roaming\npm\node_modules\karma-cli\node_modules\resolve\lib\async.js:93:22)
at C:\Users\Oliver\AppData\Roaming\npm\node_modules\karma-cli\node_modules\resolve\lib\async.js:24:18
at FSReqWrap.oncomplete (fs.js:82:15)
```

I just installed karma and tried to init a new configuration. Seems to be a problem with MINGW. The command works in the default Command Prompt.

Reproduce `karma init karma.conf.js` in Git Bash on Windows and compare it with Command Prompt. Start at `lib/init/state_machine.js`, especially `suggestNextOption`, then trace the `readline` interaction shown in the stack trace. Done means initialization completes without the `slice` TypeError in MINGW.

Written by the indexing model from the issue text.