measures.py crashes

[elisescu]

Fix this crash

 [Backend]:   File "/app/questions/services/movement.py", line 141, in calculate_period_movement_for_questions
 [Backend]:     question_movement_map[question] = serialize_question_movement(
 [Backend]:                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 [Backend]:   File "/app/questions/serializers/common.py", line 870, in serialize_question_movement
 [Backend]:     divergence = prediction_difference_for_sorting(
 [Backend]:                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 [Backend]:   File "/app/utils/the_math/measures.py", line 100, in prediction_difference_for_sorting
 [Backend]:     return sum([(p - q) * np.log2(p / q) for p, q in zip(p1, p2)])
 [Backend]:                  ~~^~~
 [Backend]: TypeError: unsupported operand type(s) for -: 'float' and 'NoneType'

Sometimes this serialization crashes and makes the whole questions page fail to load. Fix the crash so it handles gracefully cases when it cannot compute the movement.

[lsabor]

I only see issues documenting this on Dev (not Production). My understanding is that this is only because of an incompatibility between the MC Option change branch that was deployed previously and any other branch which doesn't include support for None values.

I propose that this doesn't have to be addressed at all or is addressed by manually deleting the offending data off of Dev/Play rather than any code change (would take me ~10-15 minutes).

[lsabor]

it was a data incompatability issue which is now sorted.