overview fails when a problem has no feedback
Here's the traceback:
Let's also cover this case with a test.
Traceback (most recent call last):
File "/opt/conda/envs/zesje-dev/lib/python3.6/site-packages/flask/app.py", line 1950, in full_dispatch_request
rv = self.dispatch_request()
File "/opt/conda/envs/zesje-dev/lib/python3.6/site-packages/flask/app.py", line 1936, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/opt/conda/envs/zesje-dev/lib/python3.6/site-packages/flask_restful/__init__.py", line 468, in wrapper
resp = resource(*args, **kwargs)
File "/opt/conda/envs/zesje-dev/lib/python3.6/site-packages/flask/views.py", line 89, in view
return self.dispatch_request(*args, **kwargs)
File "/opt/conda/envs/zesje-dev/lib/python3.6/site-packages/flask_restful/__init__.py", line 583, in dispatch_request
resp = meth(*args, **kwargs)
File "/app/zesje/api/statistics.py", line 211, in get
'problems': [data[p.id] for p in exam.problems],
File "/app/zesje/api/statistics.py", line 211, in <listcomp>
'problems': [data[p.id] for p in exam.problems],
KeyError: 34