libmysql/libmysql.c:
  Fix for bug#8330 "mysql_stmt_execute crashes": we need to bail out
  from mysql_stmt_execute if mysql->net is occupied with a result set of
  another statement. Otherwise on the next attempt to use net we get
  a crash, as it's freed in case of error.
tests/mysql_client_test.c:
  A test case for Bug#8330 "mysql_stmt_execute craches" (libmysql)