Make NSAssert simply an if clause to allow mismatched defaultValue

[eschramm]

Fixes https://github.com/CareEvolution/MyDataHelps-iOS/issues/1314.

While the fix is relatively simple, following the logic upstream to understand risk of regression bugs is not. Regardless, I feel confident this fixes the issue by de-escalating a mismatched defaultValue of an ORK[1]AnswerFormat (which is technically not stored there, but we pluck them out on deserialization) from an NSAssert to a simple check. I ran though the UITests as well which does a battery of tests on basic RK functionality.

Testing

Verify the following survey doesn't crash on iOS. It has a defaultValue ("garbage") which doesn't match any of the TextChoice values.

Also regression testing of survey functionality of iOS would be helpful, in particular the following:

• surveys with valid defaultValues
• navigation forward and backward to verify previous answers reappear correctly
• restoring saved surveys and validating answers restore correctly

{
  "type": "RKStudioOrderedTask",
  "name": "Survey",
  "identifier": "Survey",
  "steps": [
      {
        "identifier": "AFib",
        "type": "QuestionStep",
        "answerFormat": {
          "type": "TextChoiceAnswerFormat",
          "textChoices": [
            {
              "type": "TextChoice",
              "value": "1",
              "text": "Yes"
            },
            {
              "type": "TextChoice",
              "value": "0",
              "text": "No"
            }
          ],
          "style": "Single",
          "customField": "afib",
          "descriptionStyle": "",
          "defaultValue": "garbage"
        },
        "optional": false,
        "text": "Do you have atrial fibrillation (AFib)?"
      }
  ]
}

[mmertsock]

LGTM 🚢

Tested with the survey in this PR, and also a more complex survey with additional steps to verify navigation and state restoration.

[mmertsock]

Also didn't see anything else that we would need to update to go along with this change, and didn't find additional NSAsserts that should be addressed for this particular issue.