bug: window function in case when cause panic

[b41sh]

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• I had searched in the issues and found no similar issues.

Version

v1.2.233

What's Wrong?

window function in case when cause panic

panicked at src/query/expression/src/property.rs:333:30:
internal error: entered unreachable code: unable to merge Map(None) with Undefined

How to Reproduce?

mysql> create table tt1(a bool, b int);
Query OK, 0 rows affected (0.15 sec)

mysql> insert into tt1 values(true, 1),(false, 2);
Query OK, 2 rows affected (0.31 sec)

mysql> SELECT CASE WHEN tt1.a THEN last_value([{}, {}, {}]) OVER (PARTITION BY FALSE) WHEN tt1.a THEN [{}] END FROM tt1;
ERROR 2013 (HY000): Lost connection to MySQL server during query
No connection. Trying to reconnect...
Connection id:    19
Current database: *** NONE ***

Are you willing to submit PR?

• Yes I am willing to submit a PR!