line 181, avoiding error when version is "unknown"

Traceback (most recent call last):
  File "/home/rafael/Documents/pupil-0.3.7.4/pupil_src/player/main.py", line 440, in <module>
    main()
  File "/home/rafael/Documents/pupil-0.3.7.4/pupil_src/player/main.py", line 188, in main
    rec_version_float = int(filter(type(rec_version).isdigit, rec_version)[:3])/100. #(get major,minor,fix of version)
ValueError: invalid literal for int() with base 10: ''