Steps to reproduce

First, create a tag set with more than 20 tags of one type, e.g. 21 characters:

1. Log in

2. Browse > Tags > Tag Sets > New Tag Set

3. Fill in a title

4. Enter more than 20 tags of one type in the appropriate field, e.g. 21 characters in the "Add Characters" field

5. Press "Submit"

Second, create a gift exchange that uses the tag set and is open for sign-ups:

1. Browse > Collections > New Collection

2. Fill in required informat

3. For "Type of challenge, if any," choose "Gift Exchange"

4. Press "Submit"

5. Check "Sign-up open?"

6. Make sure the type of tag you used in your tag set is allowed in requests or offers, e.g. if your tag set uses character tags, you should be allowed to request at least one Character

7. In "Tag Sets To Use," fill in the name of the tag set you created

8. Press "Submit"

Now try to access the list of available tags:

1. Follow the "Sign-up Form" link in the sidebar

2. Use the "List [X] [Tag Type]" link

What happens

A 500 error:

What should happen

It should work.