Fix for Setting the custom properties value to null doesn't revert the value in SDM

[akgarg06]

Describe your changes

Added null check for secondary properties, so in case value is removed from UI then it will not include in builder request and remove from backend.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist before requesting a review

• I follow Java Development Guidelines for SAP
• I have tested the functionality on my cloud environment.
• I have provided sufficient automated/ unit tests for the code.
• I have increased or maintained the test coverage.
• I have ran integration tests on my cloud environment.
• I have validated blackduck portal for any vulnerability after my commit.

Single Tenant : https://github.com/cap-java/sdm/actions/runs/21616665799
Multi Tenant : https://github.com/cap-java/sdm/actions/runs/21624078165

Tested scenarios

1 - adding integer secondary type value and remove from attachment, changes reflected on backend
2 - adding date time secondary type value and remove from attachment, changes reflected on backend
3 - adding boolean secondary type value and remove from attachment, changes reflected on backend
4 - did above scenario with multiple attachment with different combinations.

[akgarg06]

gemini review

[vibhutikumar07]

gemini review