Fix exhalable cat

[microprediction]

:50:01 Submitted to sateb_4.json 310s horizon, and will do so again in 118 seconds.
Nov 23 15:50:04 Submitted to sateb_7.json 70s horizon, and will do so again in 121 seconds.
Nov 23 15:50:05 Traceback (most recent call last):
Nov 23 15:50:05 File "/home/micropredictioncrawlers/crawlers/exhalable_cat.py", line 30, in
Nov 23 15:50:05 crawler.run()
Nov 23 15:50:05 File "/home/micropredictioncrawlers/.local/lib/python3.8/site-packages/microprediction/crawler.py", line 719, in run
Nov 23 15:50:05 self.predict_and_submit(name=name, delay=delay, lagged_times=lagged_times)
Nov 23 15:50:05 File "/home/micropredictioncrawlers/.local/lib/python3.8/site-packages/microprediction/crawler.py", line 482, in predict_and_submit
Nov 23 15:50:05 scenario_values = self.sample(lagged_values=lagged_values, lagged_times=lagged_times, name=name,
Nov 23 15:50:05 File "/home/micropredictioncrawlers/.local/lib/python3.8/site-packages/microprediction/fitcrawler.py", line 118, in sample
Nov 23 15:50:05 state = self.update_state(state=state, lagged_values=lagged_values, lagged_times=lagged_times)
Nov 23 15:50:05 File "/home/micropredictioncrawlers/.local/lib/python3.8/site-packages/microprediction/sequentialcrawler.py", line 59, in update_state
Nov 23 15:50:05 machine.update(value=value, dt=dt)
Nov 23 15:50:05 File "/home/micropredictioncrawlers/.local/lib/python3.8/site-packages/microprediction/univariate/expnormdist.py", line 48, in update
Nov 23 15:50:05 move = self.params['g2'] * math.tanh(self.params['g1'] * dy / self.params['g2'])
Nov 23 15:50:05 TypeError: 'NoneType' object is not subscriptable