fix: guard against read properties of undefined errors in stx helper function

[teebszet]

🔘 PR Type

• Bugfix

📜 Background

user reported extension crashing

Issue Link: https://linear.app/xverseapp/issue/ENG-2619/crash-on-loading
Context Link (if applicable):

🔄 Changes

Does this PR introduce a breaking change?

• Yes, Incompatible API changes
• No, Adds functionality (backwards compatible)
• No, Bug fixes (backwards compatible)

Changes:

• guard against read properties of undefined errors in stx helper function

Impact:

• called from web-extension when displaying STX transactions
• also opened a PR for mobile to use this function

✅ Review checklist

Please ensure the following are true before merging:

• Code Style is consistent with the project guidelines.
• Code is readable and well-commented.
• No unnecessary or debugging code has been added.
• Security considerations have been taken into account.
• The change has been manually tested and works as expected.
• Breaking changes and their impacts have been considered and documented.
• Code does not introduce new technical debt or issues.

[github-actions]

Test this PR with npm i @secretkeylabs/[email protected]