Revision 1702974

Replace an ugly assertion caused by a corrupt working copy database with an
almost as ugly, but better to diagnose error message.

Somehow these few cases which should be completely impossible to trigger
without editing wc.db are reported as TortoiseSVN exception reports.

I explicitly add these extra checks only to the most common read operation,
as this function is usually called first and catching every invalid working
copy database is impossible without a performance and a maintenance impact.

* subversion/libsvn_subr/token.c
  (svn_token__from_word_err): Ensure NULL is handled safely.

* subversion/libsvn_wc/wc_db.c
  (column_token_err): New helper function.
  (read_info): Use column_token_err when parsing tokens.