FIO-10554: Fixed issue where if you do not set the variable in a calculation, that unexpected behavior occurs.

[travist]

Link to Jira Ticket

https://formio.atlassian.net/browse/FIO-10554

Description

If you have a calculation where you do not actually set the variable, then unexpected things occur.

For example:

if (someCondition) {
  show = false;
}

This would historically show the field since it historically would be true by default, but now it hides because the "show" variable is undefined and then returns the wrong value.

Breaking Changes / Backwards Compatibility

This resolves a breaking change between 9.x and 8.x deployments for server side behavior.

Dependencies

None

Checklist:

• I have completed the above PR template
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• My changes include tests that prove my fix is effective (or that my feature works as intended)
• New and existing unit/integration tests pass locally with my changes
• Any dependent changes have corresponding PRs that are listed above