Add empty-slug guard for creator routes

[Chucks1093]

Summary

Add a small guard for creator routes that rejects empty slug values before deeper handling.

Acceptance Criteria

• empty slug input is handled consistently
• guard is reusable from creator route flow
• behavior is narrow and easy to test

Contributor coordination: https://t.me/accesslayerorg

[shoaib050326]

@shoaib050326 has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Can you please assign this to me..

ℹ️ Repo Maintainers: To accept this application, review their application or assign @shoaib050326 to this issue.

[johnsmccain]

@johnsmccain has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Hi maintainer, I would like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @johnsmccain to this issue.

[drips-wave]

Congratulations, @shoaib050326! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

🧑‍💻 @shoaib050326: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[drips-wave]

This issue has been completed by @shoaib050326 as part of the Stellar Wave Program's 3rd Wave 🥳

😎 @shoaib050326: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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