Fix DataPathSelection behavior

Fix DataPathSelection: even if setting the file fails we want to provide it to the completer and update the example.

• self._dataPathFinder.file = file_path can fails for example if the data path is not part of the file. In this case we want the completer to be updated anyway. Else we will end up having no completer.
• same for the example. It should handle the different file valid, existing use cases directly.