"create as select" (innodb table)

Problem: code constructing "CREATE TABLE..." statement
doesn't take into account that current database is not set
in some cases. That may lead to a server crash.

Fix: check if current database is set.


mysql-test/extra/binlog_tests/binlog.test:
  Fix for bug#45998: database crashes when running
  "create as select" (innodb table)
    - test case.
mysql-test/suite/binlog/r/binlog_row_binlog.result:
  Fix for bug#45998: database crashes when running
  "create as select" (innodb table)
    - test result.
sql/sql_show.cc:
  Fix for bug#45998: database crashes when running
  "create as select" (innodb table)
    - added check if there's current database set.