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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
Not an issue since you manifestly didn't check for the input that causes this failure. And btw, with something like 5000 guys having already solved the kata, you should guess better than imagining an issue in the kata rather than in your code...
;)