NER fails to display example table in dev

[lyuyangh]

How to reproduce:

1. Pick a NER system
2. Click "analysis"
3. Click one of the fine-grained analysis bar charts

Frontend error: Cannot use 'in' operator to search for 'token_span' in undefined
This works fine on prod. This is an issue for both newly submitted systems and old systems in the DB.

[noelchen90]

This should be fixed by PR #455! Thanks for spotting this.