mariadb_dyncol_list_named() leaks the result array when a column name cannot be read

mariadb_dyncol_list_named() allocates the result array (*names) before it reads the column names from the packed dynamic column. If read_name() fails for one of the entries, the function returns ER_DYNCOL_FORMAT without freeing the array and without resetting *names:

LEX_STRING tmp;

if (read_name(&header, read, &tmp))

  return ER_DYNCOL_FORMAT;          /* *names is neither freed nor reset */