In embedded server we use result->alloc to store field data for the
result, but we didn't clean the result->alloc if the query returned
an empty recordset. Cleaning for the empty recordset enabled


libmysql/libmysql.c:
  Bug #29687 mysql_stmt_store_result memory leak in libmysqld
  
  we should clean result->alloc even if we have nothin in 'data' field