Import doesn't work with 0KB article

When trying to import a XAR file that contains an article with the size of 0KB, the message "No documents found in the selected archive" is print out. It's impossible to import any articles of the XAR archive.

I don't know how this could have been ever created, since XWiki doesn't allow users to create empty articles .... anyway, somehow there were empty articles in my XAR-export file.

Tested it with 1.3

To reconstruct: Delete the content of at least one article inside the xar-file (or create a new empty file and add an entry to the package.xml file)