After deleting the Question Group child of that group is not voided

[AchalaBelokar]

Describe the bug
After voiding a Question Group form element, error is shown on performing the encounter.

To Reproduce
Steps to reproduce the behavior:

1. Login with dinesh@dineshbootcamp
2. go to the app designer
3. go to the individual registration form delete the Question Group form element (it should have some child form elements).
4. Sync and perform individual registration
5. On click of next after page 1,
6. error is shown - Cannot read property 'concept' of undefined.

Analysis
Issue is because child form elements in a question group are not voided when the question group form element is voided.
Because of the above, the app tries to process the child form elements but breaks when trying to retrieve and use parent form element.

Expected behavior
A clear and concise description of what you expected to happen.

Test Data
Give details of example users, environment detail, username against which this issue is happening.

Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
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Developer Checklist(Developer fixing the bug should fill this checklist)

• Does the fix require extensive regression testing?
  • Yes
  • No
• Are you mentioning the required scenarios that could be affected?
  • Yes
  • No