Zend\Validator\File\MimeType warning with no params

The following code will throw 3 warnings:

```php
$mimeTypeValidator = new \Zend\Validator\File\MimeType();
```
```
Warning: array_key_exists() expects parameter 2 to be array, null given in \library\Zend\Validator
\File\MimeType.php on line 116
Warning: array_keys() expects parameter 1 to be array, null given in \library\Zend\Validator\File\MimeType.php on line 123
Warning: Invalid argument supplied for foreach() in \library\Zend\Validator\File\MimeType.php on line 123
```
removed trailing spaces
Merge pull request #4856 from giulianoriccio/patch-1

Zend\Validator\File\MimeType warning with no params
Merge branch 'hotfix/4856'

Close #4856