Running bulk text match task fails if repo is empty

[swinslow]

Appears to fail because no files means it crashes when it can't retrieve license data:

Traceback (most recent call last):
  File "upload-**********.py", line 256, in <module>
    runTasksForUpload(server, projectName, zipPath, uploadName)
  File "upload-**********.py", line 214, in runTasksForUpload
    retval = t.run()
  File "/Users/steve/programming/lftools/fossdriver/fossdriver/tasks.py", line 260, in run
    a = self._makeRealAction(licenseName, actionType)
  File "/Users/steve/programming/lftools/fossdriver/fossdriver/tasks.py", line 234, in _makeRealAction
    licenseId = self._findLicenseID(licenseName)
  File "/Users/steve/programming/lftools/fossdriver/fossdriver/tasks.py", line 224, in _findLicenseID
    self.parsedLicenses = self.server.GetLicenses(u._id, u.topTreeItemId)
  File "/Users/steve/programming/lftools/fossdriver/fossdriver/server.py", line 235, in GetLicenses
    licenses = fossdriver.parser.parseAllLicenseData(results.content)
  File "/Users/steve/programming/lftools/fossdriver/fossdriver/parser.py", line 127, in parseAllLicenseData
    options = sel.find_all("option")
AttributeError: 'NoneType' object has no attribute 'find_all'

(transferred from https://gitlab.com/swinslow/fossdriver/issues/1)