weird compilation fix
weird compilation fix

strangely enough, ?: variant does not link in some older gcc versions:

sql/sql_table.cc:6409: undefined reference to `Alter_inplace_info::ALTER_STORED_GCOL_EXPR'
sql/sql_table.cc:6409: undefined reference to `Alter_inplace_info::ALTER_VIRTUAL_GCOL_EXPR'

natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2