MDEV-4808: Assertion: trx->start_file != 0 fails in trx0trx.cc on killing CREATE TABLE query. 
MDEV-4808: Assertion: trx->start_file != 0 fails in trx0trx.cc on killing CREATE TABLE query. 

Analysis: There is debug assertion ut_ad(trx->start_file != 0); and ut_ad(trx->start_line != 0); on trx_start_low funcition at trx0trx.cc. These fields are initialized on include/trx0trx.h at function trx_start_if_not_started_xa. Thus at trx_prepare_for_mysql function should call trx_start_if_not_started_xa(trx); not trx_start_if_not_started_xa_low(trx) directly;

ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,flynn1973/mariadb-aix,ollie314/server,ollie314/server,flynn1973/mariadb-aix,ollie314/server,ollie314/server,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,flynn1973/mariadb-aix,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,davidl-zend/zenddbi,davidl-zend/zenddbi,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2,davidl-zend/zenddbi,flynn1973/mariadb-aix,davidl-zend/zenddbi