Fixed a bug causing a crash for multi-update/multi-delete
  with impossible where (bug #1860).


sql/sql_class.h:
  Fixed a bug causing a crash for multi-update/multi-delete
  with impossible where (bug #1860).
sql/sql_delete.cc:
  Fixed a bug causing a crash for multi-update/multi-delete
  with impossible where (bug #1860).
sql/sql_update.cc:
  Fixed a bug causing a crash for multi-update/multi-delete
  with impossible where (bug #1860).
mysql-test/t/multi_update.test:
  Fixed a bug causing a crash for multi-update/multi-delete
  with impossible where (bug #1860).
mysql-test/r/multi_update.result:
  Fixed a bug causing a crash for multi-update/multi-delete
  with impossible where (bug #1860).
BitKeeper/etc/logging_ok:
  Logging to logging@openlogging.org accepted