Hotfix/php54 empty

```
$ php -l src/Openl10n/Bundle/ApiBundle/Facade/TranslationCommit.php 
PHP Fatal error:  Can't use method return value in write context in src/Openl10n/Bundle/ApiBundle/Facade/TranslationCommit.php on line 67

Fatal error: Can't use method return value in write context in src/Openl10n/Bundle/ApiBundle/Facade/TranslationCommit.php on line 67
Errors parsing src/Openl10n/Bundle/ApiBundle/Facade/TranslationCommit.php
```