substr() on view returns NULL sometimes

This issue exists in InfiniDB.

This issue arose because of an anomoly seen in working_tcph_comparelogonly/partitionOptimization/vTpch22.sql

When substr is called on a view, sometimes it returns NULL

Here we select substr and acct_bal from the table. We get the expected result.
MariaDB [tpch1]> select substr(c_phone, 1, 2) as cntrycode, c_acctbal from customer where substr(c_phone, 1, 2) in ('13', '31', '23', '29', '30', '18', '17') limit 10;
--------------------+

--------------------+

--------------------+
10 rows in set, 1 warning (0.30 sec)

Here we select substr and acct_bal from the view. We get unexpected NULLs on some of the rows.
MariaDB [tpch1]> select substr(c_phone, 1, 2) as cntrycode, c_acctbal from v_customer where substr(c_phone, 1, 2) in ('13', '31', '23', '29', '30', '18', '17') limit 10;
--------------------+

--------------------+

--------------------+
10 rows in set, 1 warning (0.34 sec)

Here we select only substr from the view. We get the expected result.
MariaDB [tpch1]> select substr(c_phone, 1, 2) as cntrycode from v_customer where substr(c_phone, 1, 2) in ('13', '31', '23', '29', '30', '18', '17') limit 10;
-----------

-----------

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10 rows in set, 1 warning (0.46 sec)

MariaDB [tpch1]>