The has_video=False flag for sources doesn't seem to work

[baldurmen]

When trying to use AlsaAudioSource or the PulseAudioSource (the only two sources that have the has_video=False flag), voctocore crashes with the following error message:

"ERROR: Gst: : No src-element named 'video-foo'

Adding a test source to one of those by adding has_video=True and def build_videoport(self): does seem to fix the issue, although that's not a real fix :)