Fix - When submitting signup form, values for fields of type multi-select are not preserved if form is rejected

[roopeshbuddyboss]

#2534

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Changes proposed in this Pull Request:

Fixes #2534 .

How to test the changes in this Pull Request:

1. Create a multi-select profile field and add it to "details (signup)" field group.
2. Add some test selections for this field.
3. Open an incognito window
4. Navigate to the signup page.
5. Submit the form with an illegal handle.
6. Form should re-display, previous selections in multi-select do not appear.

Proof Screenshots or Video

https://www.loom.com/share/b1bc320d644547cb9567aecfa6869886

Other information:

• [X] Have you added an explanation of what your changes do and why you'd like us to include them?
• [ ] Have you written new tests for your changes, as applicable?
• [X] Have you successfully run tests with your changes locally?