fix: add case for SGID MyInfo when field value is missing

[wanlingt]

Problem

False positives (field values that were not missing from the constants lists) were being logged because of an erroneous SGID check. As a result, a monitor was being falsely triggered

Solution

Add separate conditionals for Singpass and SGID MyInfo values

Breaking Changes

• No - this PR is backwards compatible

Tests

Singpass MyInfo

• Submit a Singpass MyInfo form that contains the MyInfo nationality field
• Check that the field is not logged in error logs (search for meta.action like 'prefillAndSaveMyInfoFields')

SGID MyInfo

• Submit a SGID MyInfo form that contains the MyInfo nationality field
• Check that the field is not logged in error logs (search for meta.action like 'prefillAndSaveMyInfoFields')

[KenLSM]

LGTM