bug(vocabulary): fix for vocabulary management for ScalarDeclaration

[sanketshevkar]

Closes #656

When adding vobulary terms as decorators to the model, englishMissingTermGenerator failed for Scalars. Fixed the issue and modified a test.

Changes

• Optionally chained the function call to getProperties for the declarations object. As Scalars don't have properties, the function won't get called.

Author Checklist

• Ensure you provide a DCO sign-off for your commits using the --signoff option of git commit.
• Vital features and changes captured in unit and/or integration tests
• Commits messages follow AP format
• Extend the documentation, if necessary
• Merging to main from fork:branchname