It appears to be possible for the debug port to open without any tabs, so we should handle that.
It appears to be possible for the debug port to open without any tabs, so we should handle that.

nlevitt/brozzler,internetarchive/brozzler,internetarchive/brozzler,nlevitt/brozzler,nlevitt/brozzler,internetarchive/brozzler,vonrosen/umbra,nlevitt/brozzler,internetarchive/brozzler,nlevitt/brozzler,vonrosen/umbra,internetarchive/umbra