Blank track segments cause exception on statistics generation

[Andrew Gee]

If a GPX trace has an empty trkseg tag <trkseg></trkseg>, the application will fail to fully import the gpx trace file, and will throw an exception:

Traceback (most recent call last):
  File "/usr/local/lib/python2.6/dist-packages/gpxviewer/ui.py", line 300, in onTrackAdded
    self.selectTrace(trace)
  File "/usr/local/lib/python2.6/dist-packages/gpxviewer/ui.py", line 347, in selectTrace
    distance = trace.get_distance()
  File "/usr/local/lib/python2.6/dist-packages/gpxviewer/gpx.py", line 151, in get_distance
    return self._get_cached_value("distance")
  File "/usr/local/lib/python2.6/dist-packages/gpxviewer/gpx.py", line 97, in _get_cached_value
    self._walk_points()
  File "/usr/local/lib/python2.6/dist-packages/gpxviewer/gpx.py", line 85, in _walk_points
    seconds += (pointp['time'] - segment['points'][0]['time']).seconds
TypeError: 'NoneType' object is unsubscriptable

[Andrew Gee (andrewgee)]

Fix completed by not importing blank trksegs into the gpx trace object.