Set default value as empty string for model_id

[kethan1122]

Description of change

This PR sets default value of model_id as empty string when the field is not configured.

Manual QA steps

• Set the model_id to None in config and tested.

string = "hello/<model_id>/world"
config = {"singer": "io", 'model_id': None}
model_id = config.get('model_id') or ''
print(string.replace('<model_id>', model_id))

• Set the model_id to "" in config and tested.

string = "hello/<model_id>/world"
config = {"singer": "io", 'model_id': ''}
model_id = config.get('model_id') or ''
print(string.replace('<model_id>', model_id))

Above QA steps were ran using local python interpreter as it is difficult to write unit tests looking at the code structure

Risks

• Low

Rollback steps

• revert this branch

[RushiT0122]

Please mention the manual test scenarios we have covered to test the fix.

[kethan1122]

@RushiT0122 updated the PR description with Manual QA steps