#38 Ugly error message in logbook

[adam marshall]

If an attempt is made to delete a question after a user
has made an entry about that question, an ugly error
message appears:

java.sql.SQLException: ERROR:
fk_lb_entries_to_questions referential
integrity violation - key in log_book_questions still
referenced from
log_book_entries

The user should be politely informed that they cannot
delete a question after a user entry has been made.
(That seems like a reasonable course of action to me.)