Fix: prevent internal server error when deleting empty swimlane (#197)

[pranavkp71]

Fix issue #197 - deleting an empty swimlane caused an Internal Server Error.

Fix implemented:

• Added a simple check before updating related user stories to safely handle empty simlanes.
• This prevents .update() from being called when there are no linked user stories, avoiding the creas.
• Tested locally - deleting an empty swimlane now returns 204 No content without errors

[pranavkp71]

Closing this PR because the issue has already been resolved by PR #206.
Thank you, and I’ll look for another issue to contribute to