Some recordings have wrong times. Fix them so that nothing after
        loading a handwritten recording breaks.

def fix_times(self):
        """
        Some recordings have wrong times. Fix them so that nothing after
        loading a handwritten recording breaks.
        """
        pointlist = self.get_pointlist()
        times = [point['time'] for stroke in pointlist for point in stroke]
        times_min = max(min(times), 0)  # Make sure this is not None
        for i, stroke in enumerate(pointlist):
            for j, point in enumerate(stroke):
                if point['time'] is None:
                    pointlist[i][j]['time'] = times_min
                else:
                    times_min = point['time']
        self.raw_data_json = json.dumps(pointlist)