MDEV-34474 InnoDB: Failing assertion: stat_n_leaf_pages > 0 in ha_innobase::estimate_rows_upper_bound

- Column stat_value and sample_size in mysql.innodb_index_stats
table is declared as BIGINT UNSIGNED without any check constraint.
user manually updates the value of stat_value and sample_size
to zero. InnoDB aborts the server while reading the statistics
information because InnoDB expects at least one leaf
page to exist for the index.

- To fix this issue, InnoDB should interpret the value of
stat_n_leaf_pages, stat_index_size in innodb_index_stats
stat_clustered_index_size, stat_sum_of_other_index_sizes
in innodb_table_stats as valid one even though user
mentioned it as 0.