87408: Add fallback for debt total monthly net income

[maxx1128]

Note: Delete the description statements, complete each step. None are optional, but can be justified as to why they cannot be completed as written. Provide known gaps to testing that may raise the risk of merging to production.

Summary

We found out that nil values were slipping through for "total monthly net income" property for the transform. This adds fallback 0.00 values for the instances of it.

• This work is behind a feature toggle (flipper): YES
• (Summarize the changes that have been made to the platform)
• (If bug, how to reproduce)
• (What is the solution, why is this the solution?)
• (Which team do you work for, does your team own the maintenance of this component?)
• (If introducing a flipper, what is the success criteria being targeted?)

Related issue(s)

• [FSR] Bugfix for nil questions va.gov-team#87408

Testing done

Covered by existing tests

Screenshots

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What areas of the site does it impact?

(Describe what parts of the site are impacted andifcode touched other areas)

Acceptance criteria

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No error nor warning in the console.
• Events are being sent to the appropriate logging solution
• Documentation has been updated (link to documentation)
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Feature/bug has a monitor built into Datadog (if applicable)
• If app impacted requires authentication, did you login to a local build and verify all authenticated routes work as expected
• I added a screenshot of the developed feature

Requested Feedback

(OPTIONAL)What should the reviewers know in addition to the above. Is there anything specific you wish the reviewer to assist with. Do you have any concerns with this PR, why?