we changing current db temporarily and restore it when sp is created. however thd->db
in this case becomes empty string rather than NULL and so all checks of thd->db == NULL 
will be false. So if after this we'll issue create procedure sp2()... without specifying
db it will succeed and create sp with db=NULL, which causes mysqldto crash on 
show procedure status statement.

This patch fixes the problem.

it is added a check of not being empty value. When modifying SP with Admin 
application on win32 it does not pass curent database so sp is stored with
db=null which causes a crash later on show procedure status;

into mysql.com:/M50/mysql-5.0

into mysql.com:/home/psergey/mysql-5.0-nov08-push

into mysql.com:/M50/mysql-5.0

into mysql.com:/home/psergey/mysql-5.0-nov08-push

into  perch.ndb.mysql.com:/home/jonas/src/mysql-5.0-push

into mysql.com:/home/psergey/mysql-5.0-nov08-push

into mysql.com:/home/psergey/mysql-5.0-oct08-push

into production.mysql.com:/usersnfs/istruewing/autopush/mysql-5.0

into mysql.com:/home/psergey/mysql-4.1-nov08-push

into mysql.com:/home/psergey/mysql-4.1-nov08-push

into  mysql.com:/home/cps/mysql/trees/mysql-5.0-virgin

into  mysql.com:/home/cps/mysql/trees/mysql-5.0-virgin

into mysql.com:/M50/mysql-5.0

into  mysql.com:/home/cps/mysql/trees/mysql-4.1

Replace the full socket path name, not just a directory component. bug#14720

Initialized 'ptr' for a newly instantiated varstring field.
This is required by INSERT DELAYED.

No test case. This is a migration issue. There are two shell
scripts attached to the bug report. They can be used for testing.

test "length" first (otherwise when "length" is 0, the *from invalid access still triggers a Valgrind warning).
I wrote to the Valgrind authors in case this is something fixable in Valgrind (normally the
decision to issue a warning is based on the simulated CPU condition code, which should not be undefined here).

into  mysql.com:/home/mysql_src/mysql-5.0

when calculating table->null_fields.

into  rurik.mysql.com:/home/igor/dev/mysql-5.0-0

into mysql.com:/home/psergey/mysql-5.0-oct03-push

  Always use bundled zlib

into  rurik.mysql.com:/home/igor/dev/mysql-5.0-0

into  mysql.com:/my/mysql-5.0

into  mysql.com:/home/cps/mysql/trees/mysql-5.0

into  mysql.com:/my/mysql-5.0

(Main reason for reordering was to get rid of compiler warnings for order of element initialization)

into  neptunus.(none):/home/msvensson/mysql/mysql-5.0