Internal server error after adding a donation

[cellio]

The donations server fails with "Internal Server Error" if there is an entry in the donations table. I've tried a bunch of permutations, including amounts with and without currency symbols. I can't find a way to enter data that doeesn't cause a failure.

Here's an example from the admin console:

Public name: Another test
Message: Keep up the good work :-)
Date: 2022-01-01
Amount: $5.00
Link: (a valid link to a Stripe transaction)

When I deleted that entry, the page worked again (with no data, of course):

I then created a simpler entry: name, message, date, amount, but no link. Failed.
I removed the amount: failed.
Then the message: failed.
Then the date (so there is now only a name): failed.
Removed even the name: failed.

Removed the now-empty entry: worked again.

This is a blocker for publicly thanking our donors.