Running tests on Windows caused this error:
```
B:\Projects\Parse Server\parse-server\spec\FileLoggerAdapter.spec.js:38
expect(results[0].message).toEqual('testing info logs');
^
TypeError: Cannot read property 'message' of undefined
at B:\Projects\Parse Server\parse-server\spec\FileLoggerAdapter.spec.js:38:26
at ParsePromise.<anonymous> (B:\Projects\Parse Server\parse-server\src\Adapters\Logger\FileLoggerAdapter.js:9:17440)
at ParsePromise.wrappedResolvedCallback (B:\Projects\Parse Server\parse-server\node_modules\parse\lib\node\ParsePromise.js:139:41)
at ParsePromise.resolve (B:\Projects\Parse Server\parse-server\node_modules\parse\lib\node\ParsePromise.js:72:36)
at resolveOne (B:\Projects\Parse Server\parse-server\node_modules\parse\lib\node\ParsePromise.js:471:29)
at ParsePromise.object.then.errors.(anonymous function) (B:\Projects\Parse Server\parse-server\node_modules\parse\lib\node\ParsePromise.js:480:13)
at ParsePromise.wrappedResolvedCallback (B:\Projects\Parse Server\parse-server\node_modules\parse\lib\node\ParsePromise.js:139:41)
at ParsePromise.resolve (B:\Projects\Parse Server\parse-server\node_modules\parse\lib\node\ParsePromise.js:72:36)
at ReadFileContext.callback (B:\Projects\Parse Server\parse-server\src\Adapters\Logger\FileLoggerAdapter.js:9:16189)
at FSReqWrap.readFileAfterOpen [as oncomplete] (fs.js:303:13)
```
Rest of the tests could not be run as the test runner would break here. This change adds a check to fail when the FileLoggerAdapter returns an empty array from here: https://github.com/ParsePlatform/parse-server/blob/master/src/Adapters/Logger/FileLoggerAdapter.js#L191
Regarding the cause of the error itself, it is due to different filename separators in *nix and Windows. The FileLoggerAdapter would not save logs (have not tested this). This is a separate issue and should also be fixed.
