Improvements

Bugfixes

Do not show borders above/below the message in registration emails unless both the header and body blocks are used (#3151)
Roll-back the database transaction when an error occurs.
Fix rendering of the LaTeX error box (#3163)
Fix "N/A" being displayed in a survey result if 0 is entered in a number field
Fix "N/A" not being displayed in a survey result if nothing is selected in a multi-choice select field
Fix error when using target_* placeholders in abstract notification emails for actions other than "Merged" (#3171)
Show full track title in tooltips on abstract pages
Show correct review indicators when a reviewer still has to review an abstract in a different track
Fix unicode error when searching external users in an LDAP backend (indico/flask-multipass#19)