fix: ValidationError in ChannelInstance Constructor

[thenasty1337]

Fix Applied to ChannelInstance Constructor:

Added a check to ensure livestream.categories[0].description is a string. If not, it defaults to 'Default category description'.
Prevents ValidationError caused by type mismatch in channel data.

Testing:

Conducted tests to confirm the fix resolves the issue.
No additional side effects observed in related functionality.

[zSoulweaver]

Thanks for taking the time to contribute 🤘

Cheers for this, however I would prefer to implement this directly in the DTO interface, if possible, to keep everything contained by using @deepkit/type.

Either we can mark the field as an optional which will have the string | undefined type and we leave it up to the end use to their own undefined check. Alternatively, if we want to set a default value instead of exporting an interface we can export a class where we can define default values, it works much the same with @deepkit/type.

I'll have a look later after work today and get back to you.