aggregate.py should ignore empty scan-data files

ERROR[Sat Jan 11 06:40:03 2014]:Exception during aggregate: empty string for float()
Traceback (most recent call last):
  File "/home/bwscanner/torflow/NetworkScanners/BwAuthority/aggregate.py", line 876, in <module>
    main(sys.argv)
  File "/home/bwscanner/torflow/NetworkScanners/BwAuthority/aggregate.py", line 424, in main
    timestamp = float(fp.readline())
ValueError: empty string for float()

Could it be that we have a race here?

$ cat .git/refs/heads/master 
229e5e64680a1a3caf496ce2c1e5d064b5edd080
$ git submodule status
 4fdd2031e6b231ed4bbaa79940f67e9b8f691382 TorCtl (2013-10-16)