OEA player: Multiple choice question propType errors

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When testing an assessment using the following default settings in the _head.html layout partial:

    bank:          "assessment.Bank%3A586eac6ced849b30a4ecc5d9%40ODL.MIT.EDU",
    assessment_offered_id: "assessment.AssessmentOffered%3A58c6d67eed849b1a873454ab%40ODL.MIT.EDU"

the user gets a propType warning when selecting an answer option for a multiple choice question

Warning: Failed prop type: Invalid prop `responses[0][0]` of type `string` supplied to `Assessment`, expected `object`

However. The user can still successfully save the question.