Emojis in application lead to Application error

[jancborchardt]

I just wanted to submit our Nextcloud conference, but on clicking »Preview Event« in https://diversitytickets.org/events/new it took a long time to load and then I get a Heroku application error:

For debugging I removed all emojis from the application and now it seems to work. All submission details / form fields are at https://github.com/nextcloud/server/wiki/Diversity-Tickets, for testing.