Database error on event registration when event title is too long

When you create an event with a very long title, and then an online registration page for this event, a database error is happening preventing any registration to happen and not displaying any feedback on-screen - just a blank page.

In the database, the civicrm_participant.source field is VARCHAR(128), and the civicrm_event.title field is VARCHAR(256).

When an online registration is created, the string "Online event registration: " is added to the event title and stored in the participant source field. When the event title is longer than 110 chars or so, this will create a database error.

The solution is to summarize the event title when adding to the source, so if longer than 100 chars, take the first 97 chars and add "..." before adding to the participant source.