#79 Adding a directory with a 0 length file fails

[Troels Larsen]

Steps to reproduce:
1. Find directory with several media files
2. Add a new file of 0 length (obviously invalid file)
3. Add the directory to the database

Expected result: Mediatomb will share all media in the folder except the invalid file(s).
Actual result: Mediatomb only shares some of the media in the folder, apparently stopping after running into the invalid file.