Fix randomization

[eu9ene]

The exception has occurred in prod for client id hash 0ace1ca2a3519332ab93e76a049fe74091fa8fc9063399caa8545dd23f93de5c and many others.

"Traceback (most recent call last):
File "/opt/conda/envs/taar-37/lib/python3.7/site-packages/flask/app.py", line 2292, in wsgi_app
response = self.full_dispatch_request()
File "/opt/conda/envs/taar-37/lib/python3.7/site-packages/flask/app.py", line 1815, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/opt/conda/envs/taar-37/lib/python3.7/site-packages/flask/app.py", line 1718, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/opt/conda/envs/taar-37/lib/python3.7/site-packages/flask/_compat.py", line 35, in reraise
raise value
File "/opt/conda/envs/taar-37/lib/python3.7/site-packages/flask/app.py", line 1813, in full_dispatch_request
rv = self.dispatch_request()
File "/opt/conda/envs/taar-37/lib/python3.7/site-packages/flask/app.py", line 1799, in dispatch_request
return self.view_functionsrule.endpoint
File "/app/taar/plugin.py", line 229, in recommendations
client_id=client_id, limit=TAAR_MAX_RESULTS, extra_data=extra_data
File "/opt/conda/envs/taar-37/lib/python3.7/site-packages/markus/main.py", line 510, in _timer_decorator
return fun(*args, **kwargs)
File "/app/taar/recommenders/recommendation_manager.py", line 109, in recommend
results = reorder_guids(results, limit)
File "/app/taar/recommenders/randomizer.py", line 42, in reorder_guids
choices = np.random.choice(guids, size=size, replace=False, p=probabilities)
File "mtrand.pyx", line 922, in numpy.random.mtrand.RandomState.choice
ValueError: probabilities are not non-negative